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Applied TechnologyLevel 6

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2 • Applied Technology

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Applied Technology • 3

INTRODUCTION

Hi! Let me introduce myself to you. I am EdWIN,and I will be your friendly guide through this study.Now, you may have met me before in a different courseor in an earlier level. If you have, I hope that you havefound that I am not too tough of a taskmaster. Lookfor me to pop up every now and then with a tip, hint,or maybe even a quiz question or two!

You are about to begin Applied Technology, Level 6.If you have already completed Level 5, you know thatit wasn’t too difficult. This level will cover the basicsonce again for your review. The main difference willbe that the exercises will be more difficult. The greatthing about this type of learning is that you generallycan set your own pace. Consequently, you will not haveto move on until you feel you have learned the materialto your satisfaction.

As in previous levels, we will be studyingthermodynamics, fluid dynamics, electricity, andmechanics.

So, if you are ready, so am I. Turn the page and let’sbegin!

Hi, I’m EdWIN!


Problem-Solving Strategies

The basic components of effective problem-solving strategies are:

• Identifying the problem (“What is the goal?” and “What limits does the goalimpose?”)

• Analyzing and interpreting data (reading a gauge, interpreting a printout).This includes identifying and disregarding nonessential data.

• Exploring and evaluating solutions (“What options are available?” and “Whichoption is best, taking into account many variables, including cost, time, humanresources, materials, environment, and expertise?”)

One well-known problem-solving model is the IDEAL* model. The IDEAL modelwas designed as an aid for teaching and improving problem-solving skills. TheIDEAL process includes the following steps:

I = Identify the problem (determine what needs to be done).D = Define and represent the problem (sharpen and clarify the boundaries).E = Explore alternative approaches (analyze and evaluate alternatives).A = Act on a plan (determine the logical steps to be used and how to progress

through the steps).L = Look at the result (determine whether or not the plan worked).

The exercises in this workbook guide learners through the IDEAL problem-solvingprocess.

* The IDEAL Problem Solver: A Guide for Improving Thinking, Learning, and Creativity , © 1984. Permission for use granted by W.H. Freeman and Company/Worth Publishers, all rights reserved.

STRATEGIES


Problem-solving strategies are critical to any instruction aimed at improving alllevels of applied technology skills. To be an effective technological problem solver,you need to be able to do the following:

• Understand cause-effect relationships (What parts of systems affect and areaffected by other parts?)

• Make comparisons (What commonalities and differences do systems have?)• Recognize probable outcomes (How will the system react to a specific action?)• Predict what should happen next (Based on what has been observed, what is

known about a specific system, and what is known about related scientificprinciples, make a prediction about what will happen next.)

• Judge spatial relationships (Visualize how a system operates and mentally rotatesystem parts to solve problems within a given system.)

• Notice what appears out of place (Observe a malfunctioning system in operationto determine what is not working correctly.)

Course Strategies

The best way for me to help you be an effective problem solver is to give youopportunities to develop and refine your problem-solving skills. Therefore, I willuse the following strategies:

• I will mimimize instructions so that you are encouraged to invent innovativeways to accomplish the tasks.

• I will provide you with a variety of materials from which to choose.• If you have questions about the exercises, reread the beginning instructions.

This strategy encourages you to figure out how to use the materials to reachyour goal.

• You have plenty of time to explore. As long as you are actively engaged, learningis taking place. If ample time is allowed, you will be able to do more in-depthinvestigation. Thinking about a problem is part of learning.

• I encourage you to share ideas with others. This strategy reflects how peoplesolve problems in the workplace — with input from others. Most problem-solving activities lend themselves to having you work individually, but you areencouraged to seek others’ input.

STRATEGIES


BASIC SCIENTIFIC PRINCIPLES

Applied Technology focuses on:

• Principles related to power sources – for thermal,fluid, electrical, and mechanical systems.

• Principles related to flow – for thermal, fluid,electrical, and mechanical systems.

• Principles related to pressure – for thermal, fluid,electrical, and mechanical systems.

• Principles related to resistance – for thermal, fluid,electrical, and mechanical systems.

Some basic scientific principles involved with energysources, flow, pressure, and resistance follow:

Bernoulli’s principle: The faster the flow of air or fluid, the lower the pressure.

Boyle’s law: For a certain amount of gas, at a constant temperature, as the pressure (P)increases, the volume (V) of the gas decreases so that P times V is constant (k). (PV=k).

Charles’ law: For a certain amount of gas, at a constant pressure, as the absolutetemperature of the gas increases, the volume of the gas also increases. Mathematicallythis is: Volume (V) divided by temperature (T) equals a constant (k). V/T=k Thetemperature must be on an absolute scale that is in reference to absolute zero.

Hooke’s law: The greater the force exerted on an object, the more it will be moved. Forexample, the heavier the weight hanging from a spring, the more the spring will bestretched.

Newton’s laws of motion:• An object will remain at rest or in uniform motion unless acted upon by an

outside force.• When a force acts upon an object, it changes the momentum of that object,

and this change is proportional to the applied force and to the time that it actsupon the object.

• Every action (force) is followed by an equal and opposite reaction (force).

Ohm’s law: Current is directly proportional to the voltage and inversely proportional tothe resistance.

Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally atall other points, and is always at right angles to the confining surfaces.

BASIC PRINCIPLES


LESSON 1 Thermodynamics

LESSON 2 Fluid Dynamics

LESSON 3 Electricity

LESSON 4 Mechanics

LESSON 5 Posttest

REFERENCES Test-Taking TipsBasic Scientific PrinciplesBibliographyAnswers to Pop Quiz Questions

OUTLINE


THERMODYNAMICS

Thermodynamics is a pretty complicated soundingword, isn’t it? It is a very complicated science. There isa lot that can be learned about it. But for our purposes,we are not going to try to become experts in the subject!We do want to learn the basics of the science. If youfind yourself in an employment situation that requiressome knowledge of the subject, you will have theconfidence to apply what you have learned. Theproblems at this level will be more difficult than thoseat previous levels. But, don’t worry; you’ll be able tocomplete them.

All matter is made up of particles that are in constantmotion. This motion manifests itself as the form ofenergy called heat. The study of heat is calledthermodynamics. Now, that wasn’t so hard, was it?There are two basic laws of thermodynamics.

Basic Laws of Thermodynamics

1. Energy cannot be created or destroyed.

2. Heat energy always flows spontaneously fromhot to cold.

LESSON 1

Q

Next time I play I willwear light-colored

clothing!


Some other generalizations that can be made aboutheat include:

• Heat travels through conductors such as metal betterthan it travels through insulators such as brick orwood. For example, you know that if you stir boilingwater with a metal spoon, it will soon heat up tothe point where you cannot touch it. If you stirboiling water with a wooden spoon, you can stir itindefinitely without it getting too hot to touch.

• Dark-colored surfaces absorb more heat than light-colored surfaces.

• Rough or dull surfaces absorb more heat thansmooth or shiny surfaces.

• When friction causes heat, the object that is inconstant contact gets hotter than the movableobject.

In this lesson we will be specifically concentratingon car air-conditioning. Several scientific principles areinvolved in these problems including latent heat,evaporation, condensation, and change of state ofmatter.

Let’s start by describing the basic operation of a carair-conditioning system. I know you are going to say,“Obviously, it is to cool the passenger compartment ofthe vehicle!” Yes, I know that already. But what does itactually do, scientifically speaking? The system takesrefrigerant from the gas phase to the liquid phase andreturns it back to a gas. Each time the refrigerantchanges state, heat is either absorbed or released.

LESSON 1


Refer to Diagram A. The parts of the system arelabeled and the airflow is marked with arrows so thatyou can follow the entire operation from start to finish.Following the diagram, I am going to list the majorparts of the system for you and describe their functions.

LESSON 1

Diagram A

This diagram was provided by and used with the permission of Deere & Co.


Compressor

This device pressurizes the refrigerant. Notice inthe drawing that the compressor contains what looksvery similar to a standard piston. Basically, that is exactlywhat it is! This piston pressurizes the gas. The refrigerantis commonly called Freon. Most of you are aware thatwhen the Freon gets low, the air conditioner cools lessand less. Many times this is the cause of malfunctioningsystems, and the missing Freon simply needs to bereplaced. If the compressor itself is not functioningproperly, look out! It could be that there is some typeof break in the seal or other cause. The compressor hasto be completely sealed or the gas will be forced outthrough the leak, therefore causing less pressurized gasto flow into the condenser. This can cause thecompressor to work overtime and literally “burn up”the device. This is a major repair expense.

Compressor clutch

This device allows the compressor to turn when itis engaged. This works the same as the clutch in amanual shift car. When you press in the clutch pedal,this allows you to put the car in gear or change gears.What happens when you try to engage the transmissionwithout pressing in the clutch pedal? Yes, that terriblegrinding noise that makes you wince as you visualizethe teeth on the gears being ground off! Big expense!Well, the clutch on the air-conditioning system worksthis way, except that you don’t have to remember topush in a pedal to engage your air conditioner. All youdo is flip a switch on the front panel of your car whichwill engage the clutch according to the setting on thethermostat.

LESSON 1


Condenser

This changes the refrigerant vapor to liquid. Therefrigerant comes in a gas form. As I stated before, thecompressor does just what it sounds like. It compressesor pressurizes the gas refrigerant. Then, the condenserchanges the gas into a liquid in order for it to flowthrough the system and cool your car.

Expansion valve

This valve reduces refrigerant pressure before itenters the evaporator. The pressure created by thecompressor causes the gas to condense and keeps theliquid from boiling. The reduction of pressure allowsthe liquid to boil. The boiling or evaporation processrequires heat, which comes from the liquid itself,resulting in cold vapor. The cold vapor then takes heatfrom the metallic fins located on the evaporator. Oncethe compressor shuts off and the rest of the liquidevaporates, the pressure in both sides of the systemequalizes; thus, the evaporator must be able towithstand high pressure.

Evaporator

An evaporator consists of a heat exchanger in whichthe liquid refrigerant is evaporated, taking its heat fromits environment. Hot liquid enters through theexpansion valve and boils, heat is transferred from themetallic fins to the refrigerant. A blower motor is thenused to move air across the evaporator, which dispersescool air.

LESSON 1


Thermostat switch

This is the mechanism I mentioned that engagesthe clutch. When you turn on your air conditionerand set the temperature that you want, the thermostatdetects the temperature in the car. If it is warmer thanthe setting, it automatically engages the clutch and startsthe cooling system. This is the same way a thermostatworks in a building’s central heat and air system. Onceit has reached the temperature you have set, it turnsoff. Try this yourself by turning on your car’s air-conditioning system. (Be sure to turn off the radio androll up your windows so that you can hear!) Then, listento the compressor engage and disengage as thethermostat switch turns on and off. The fan will beblowing all the time, but the actual cooling will shutoff and on according to the thermostat reading andthe automatic switch.

Accumulator dryer

This device removes moisture and stores extrarefrigerant.

OK, have you studied the diagram closely? Haveyou identified the parts of the system that I described?Do you understand their functions? If not, study thediagram again and reread the descriptions. This willhelp you to comprehend the basic function of thesystem.

Now, let’s try an exercise.

LESSON 1

This removes moisture!


EXERCISE – CAR AIR CONDITIONER

Instructions: Read the following scenario and refer to the diagram of the air-conditioningunit as you answer the following questions.

Scenario

A customer brings in a car and says that the air conditioneris not working. Specifically, on hot days it does not get coolenough. The customer had the car’s air-conditioning systemrecharged within the last week. There is also a clicking soundcoming from under the hood. Your supervisor asks you todiagnose the problem and suggest a solution.

Identify the problem

1. What have you been asked to do?

a. Determine why the air conditioner is not working properly.b. Determine why the car is overheating.c. Determine why the air-conditioning is not working properly and

discuss it with your supervisor.d. Fix the air-conditioning system.e. Recharge the air-conditioning system.

Define the problem

2. The problem in the system could be that:

a. the blower motor on the evaporator is not working properly.b. the magnetic clutch is not engaging properly.c. the refrigerant level is low.d. the condenser is clogged.e. the fan belt is broken.

LESSON 1


3. To identify the cause of the malfunction, you would NOT need to:

a. check the coil in the magnetic clutch.b. see if the filter in the accumulator dryer is clogged.c. check the coolant thermostat.d. inspect the temperature-sensing bulb.e. check the fan belts.

Explore alternatives

4. To isolate the problem, you would FIRST:

a. check the magnetic clutch coil.b. see if the blower motor evaporator is running.c. check for a clogged expansion valve.d. check for a loose accumulator dryer.e. check for a refrigerant leak.

Act on a plan

5. Below are observations made of the system. Which would indicatean existing problem?

a. There is a loose belt on the compressor.b. The expansion valve is not clogged.c. There is no continuity in the clutch coil.d. The pressure on the high side is 190 psi; the pressure on the low

side is 30 psi.e. The fan belt is frayed.

LESSON 1


6. To correct the problem, you would:

a. add refrigerant.b. change the expansion valve.c. change the compressor.d. replace the magnetic clutch coil.e. replace the refrigerant.

Look at the result

7. If the problem has NOT been corrected, which of the following wouldyou expect?

a. The air-conditioning has plenty of refrigerant.b. There will be no clicking sound under the hood.c. The air-conditioning system cools the car on cool days.d. The air-conditioning system cools on hot days.e. The air-conditioning system needs to be recharged at this time.

LESSON 1

IDEAL


ANSWERS TO EXERCISE

1. What have you been asked to do?

Answer: c. Determine why the air-conditioning is not working properlyand discuss it with your supervisor.

2. The problem in the system could be that:

Answer: b. the magnetic clutch is not engaging properly.

3. To identify the cause of the malfunction, you would NOT need to:

Answer: c. check the coolant thermostat.

4. To isolate the problem, you would FIRST:

Answer: a. check the magnetic clutch coil.

5. Below are observations made of the system. Which would indicatean existing problem?

Answer: c. There is no continuity in the clutch coil.

LESSON 1


6. To correct the problem, you would:

Answer: d. replace the magnetic clutch coil.

7. If the problem has NOT been corrected, which of the following wouldyou expect?

Answer: e. The air-conditioning system needs to be recharged at thistime. (Add refrigerant.)

LESSON 1

Time to move on to fluid dynamics …


IDEAL


FLUID DYNAMICS

Before we get into the specifics of this lesson, I willrepeat some basic principles that we addressedpreviously. This is to refresh your memory and if youare starting with me on this level, this will give you anopportunity to review the basics.

Some basic scientific principles involved with energysources, flow, pressure, and resistance appear below:





Newton’s laws of motion• An object will remain at rest or in uniform motion unless acted upon by an outside

force.• When a force acts upon an object, it changes the momentum of that object, and

this change is proportional to the applied force and to the time that it acts uponthe object.


Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally atall other points and is always at right angles to the containing surfaces.

LESSON 2


Q

#Other generalizations that can be made about fluid are:

Concerning pressure

• The amount of pressure exerted by a fluiddepends upon the height and the density ofthat fluid and is independent of the shape ofthe container that is holding the fluid.

• The deeper the fluid, the greater the pressureit exerts.

• The denser the fluid, the greater the pressureit exerts (salt water is denser than fresh water).

• Fluids seek equilibrium - they seek their ownlevel; a fluid will flow from a place of highpressure to a place of low pressure.

• A fluid can never rise higher than its sourcewithout an external force (a pump).

Concerning evaporation

• The higher a liquid’s temperature, the fasterit will evaporate.

• The lower a liquid’s pressure, the faster theliquid will evaporate.

• The more area of liquid that is exposed toair, the faster the liquid will evaporate.

• The more circulation of air above a liquid,the faster the liquid will evaporate.

LESSON 2


_Concerning boiling point

• Increased pressure on a liquid raises theliquid’s boiling point.

• Decreased pressure on a liquid lowers theliquid’s boiling point.

OK, now that we have reviewed the basics, let’sdiscuss the details of this level.

We will be concentrating on cooling systems withtanks. The primary principles involved are flow rate ofliquids, pulley systems, and open systems. There is anequation used to determine flow rate. Before you panicat this thought, it is not difficult, and I know you cando it!

Flow rate is equal to volume divided by time.The equation looks like this: Qv = V/t.

If you remember equations from school, you knowthat anytime there is a forward slash (/) betweennumbers or letters, it means to divide by the secondnumber.

LESSON 2


Let’s look at an example to understand this moreclearly. If you have a quart of water (volume), and ittakes two minutes for the water to flow out of acontainer (time), then you divide one quart by twoand you reach a flow rate of 1/2 quart per minute. Theformula would be written like this:

Qv = V/t or

Substitute the numerics for the letters and write theformula as follows:

Qv = 1/2

Then, do the math. Divide 2 into 1 to get youranswer.

Qv = 1/2 quart per minute.

The flow rate (Qv) then would be 1/2 quart perminute.

Fluids will flow from a place of high pressure to aplace of low pressure. An electric motor or the force ofgravity can provide the high pressure area. Fluid willflow along any path that is available to it. You see thisprinciple anytime it is raining and the water naturallyflows downhill. That’s because gravity will force it inthat direction. You can also see the principle of “thepath of least resistance” if you watch how the waterflows in certain directions, such as through gullies orlow areas.

LESSON 2

Qv =

V

t


For example, if you have a gravel driveway, you cansee how your driveway always washes out in the sameplaces. The ruts and gullies made by the water flowwill get deeper with time.

Large pipes have low pressure while smaller pipeshave greater pressure. You may be familiar with thisconcept. Why do you have small diameter pipes thatare used to send water into your home? If you had largerpipes, your water pressure would be significantlyreduced. In contrast, the pipes that drain the water orsewer system out of your home are very large indiameter. Why? This is to allow easy flow when youdrain the water from your bathtub or sink. What wouldhappen if you had the small diameter pipes hooked tothe drain system? For one, it would take forever foryour bathtub to empty!

Net flow is equal to the input flow minus the outputflow. When fluid resistance is reduced, flow rate isincreased if the pressure is constant. Fluids are typicallynon-compressible.

Now, wait a minute, you might be saying. Don’twe use hydraulic pressure to send fluids through asystem? Yes, you would be right; but, the fluid itself isnot being compressed. It is simply being forced bypressure to do specific work. Let’s discuss this a littlefurther. As you know, gas can be compressed. This isbecause in a gaseous substance, the molecules are spreadout in the container. Fluid molecules are morecondensed. While the gas can be compressed to takeup a smaller space, the fluid simply has no room to becompressed.

LESSON 2


Thinking Activity

Suppose you have a container that has four equal-sized holes placed verticallyin the side. If you fill the container with water, which of the streams ofwater would be forced out the farthest from the container?

Remembering the principle that pressure is greaterat the lowest point, you would know that the bottomhole would produce the stream the farthest from thecontainer. Look at this logically. There is a greaterdistance from the bottom hole to the top of the fluidin the container. Therefore, there is more pressure beingapplied to the bottom hole. Since the greatest pressurewould flow to the lowest point, the bottom hole wouldbe the answer.

LESSON 2


Thinking Activity

Suppose you have two containers of the same size, but with different sizeholes in each. What will happen when you fill the containers with water?Which stream of water will flow the farthest from its container?

This exercise goes back to the example that I gaveyou earlier of your home water system. The smallesthole will have greater pressure. Therefore, the streamof water will be forced farther from the container thanthe container with the larger hole.

This next exercise will focus on density of fluids.

LESSON 2


Thinking Activity

Suppose you have two containers with holes of the same size. You fill onewith water and the other with oil. Which one will force the fluid fartherfrom the container, the one with the water or the one with the oil?

In general, water is more dense and therefore,heavier than oil. The water will create more pressureand travel a greater distance than oil.

Just for comparison sake, which one would gofarther if the container with the oil contained heavycrude oil which exerted a greater pressure than the onewith the water?

Exactly as you thought, the opposite would happen.The oil would be pushed farther simply because it isunder greater pressure.

LESSON 2


Facts

Volume flow rate = Volume displaced divided by elapsed time. Qv = V/t

Net flow rate = Input rate minus output rate

4 quarts = 1 gallon

60 minutes = 1 hour

OK, now that we have looked at some diagramsand have done some thinking exercises concerningthem, let’s try some exercises dealing with flow rate.This is where you will need to use your formula. Doyou remember it? Flow rate is volume divided by time.Qv = V/t. Using this formula, calculate the flow rates.Remember that net flow rate is determined bysubtracting the output rate from the input rate.

Now, I am going to give you the answers, but don’tpeek before you try to solve these problems.

LESSON 2

Pop Quiz:Define compressor.


EXERCISE – CALCULATING FLOW RATE

Instructions: Use the facts provided to answer the following questions. Round answers tothe nearest hundredth.

1. If 200 gallons of fluid are delivered into a reservoir in 14 minutes,what is the flow rate?

____________________________________________________________

____________________________________________________________

2. A hose delivers water into a fountain at a rate of 0.75 gal/min. Thewater flows from this fountain to other components at a rate of 0.25gal/min. What is the net flow into the fountain?

____________________________________________________________

____________________________________________________________

3. A 150-gallon water tank can be filled at a flow rate of 3 gal/min. Howlong will it take to fill the tank?

____________________________________________________________

____________________________________________________________

LESSON 2


LESSON 2

POP QUIZ:Name the five steps of the IDEAL problem-solving strategy.

1. ______________________________________________

2. ______________________________________________

3. ______________________________________________

4. ______________________________________________

5. ______________________________________________


ANSWERS TO EXERCISE

1. If 200 gallons of fluid are delivered into a reservoir in 14 minutes,what is the flow rate?

Answer: Qv = V/tQv = 200 gal/14 minQv = 14.29 gallons per minute

2. A hose delivers water into a fountain at a rate of 0.75 gal/min. Thewater flows from this fountain to other components at a rate of 0.25gal/min. What is the net flow into the fountain?

Answer: Input flow = .75 gallons per minuteOutput flow = .25 gallons per minuteNet flow rate = 0.75 gal/min - 0.25 gal/minNet flow = 0.5 gallons per minute

3. A 150-gallon water tank can be filled at a flow rate of 3 gal/min. Howlong will it take to fill the tank?

Answer: Did this one seem more difficult? If you substitute the numbersfor the equation letters, you found that you were given theflow rate and the volume. So, which factor was theunknown? … the time. In this one you must turn the formulaaround a bit to figure it out.

t(time) = V(volume)/Qv(flow rate)t = 150 gal/3 gal per minutet = 50 minutes

How did you do on those exercises? If you hadtrouble, go back and review as much as you need beforeproceeding to the next problem.

LESSON 2


EXERCISE – COOLING SYSTEM WITH TANK

Instructions: Read the following scenario and refer to the diagram as you answer the followingquestions.

Scenario

At your place of employment, the cooling system has a10-horsepower motor running a positive displacement pumpat twice the speed of the motor (see diagram). The motor usesa 10˝ driving pulley and a 5˝ driven pulley. This system issupplying a 32-quart cooling tank that is 3´ tall. This tanksupplies two machines. The tank is 33% full. It takes 250minutes to finish filling the tank. Your systems operator asksyou to run a system check. You find that the flow meterreadings are accurate and you get the following resistance.

______________________________________METER FLOW RATE

______________________________________A 1

______________________________________B .5

______________________________________C 3

It is your responsibility to analyze the system and report tothe systems operator.

Cooling System

��

LESSON 2


Identify the problem

1. What is your assignment?

a. to evaluate the systemb. to determine whether the system is outdatedc. to determine whether the horsepower of the motor is correctd. to repair the systeme. to clean the cooling tank

Define the problem

2. What do you need to do to evaluate this system?

a. Replace the pump.b. Clear the lines of any clogs or blockages.c. Calculate the expected flow rate as compared to the meter

readings.d. Calculate the wattage of the motor.e. Determine the gear ratio between the motor and the pump.

Explore alternatives

3. What factors could account for the discrepancy between the actualflow rate and the meter readings?

a. The belt on the pulley is slipping.b. The cooling tank is not level.c. The pump is not running properly.d. There is a leak ahead of Meters A and B.e. There is a leak in Machines A and/or B.

LESSON 2


LESSON 2

This page is intentionally left blank.


Act on a plan

4. What is the BEST thing for you to do with this information?

a. Report to the systems operator that one of the machines isleaking.

b. Replace the motor.c. Report to the systems operator that the system is functioning

properly.d. Report to the systems operator the exact location of the leak in

the line.e. Change the speed of the pump to increase the fill rate to the

cooling tank.

Look at the result

5. After you gave the report to the systems operator, a certified repairperson sealed the leak in the cooling tank. How will you verify thatthe system is operating properly?

a. Recalculate the flow rate for the cooling tank.b. Measure the motor voltage.c. Recalculate the motor’s horsepower.d. Verify that the lines have no blockages.e. Recalculate the horsepower for the motor.

LESSON 2


ANSWERS TO EXERCISE

1. What is your assignment?

Answer: a. to evaluate the system

2. What do you need to do to evaluate this system?

Answer: c. Calculate the expected flow rate as compared to the meterreadings.

3. What factors could account for the discrepancy between the actualflow rate and the meter readings?

Answer: d. There is a leak ahead of Meters A and B.

4. What is the BEST thing for you to do with this information?

Answer: d. Report to the systems operator the exact location of theleak in the line.

5. After you gave the report to the systems operator, a certified repairperson sealed the leak in the cooling tank. How will you verify thatthe system is operating properly?

Answer: a. Recalculate the flow rate for the cooling tank.

LESSON 2


Before we complete fluid dynamics, let’s considerhydraulics. Machines that make use of pressure in aliquid are called hydraulic machines. You probablyrecognize the term from common applications such ashydraulic brakes or hydraulic lifts.

The working mechanism in a hydraulic systemcontains a set of two or more cylinders containingpistons and connected by pipes that contain hydraulicfluid. Force is applied to the main cylinder (often calledthe master cylinder) which raises the pressure of thefluid throughout the system. This action causes pistonsin the other cylinders (slave cylinders) to create a usefulforce. The amount of force is dependent upon thediameter of the slave cylinders and the pressure applied(psi). Pressure may be applied by a power-driven pump(hydraulic lift ) or a manual pump (floor jack).

If the psi is constant, the wider the slave cylinder,the greater the force applied and the shorter the distancemoved. So, a narrow slave cylinder moves a largedistance with reduced force.

LESSON 2


Let’s look more closely at a hydraulic lift. This typeof lift is used in a garage when an automobile is raisedfor inspection. Its force is accomplished by hydraulicseven though it contains only one piston. A compressorpumps air into an oil reservoir increasing the pressureof the oil. This oil reservoir acts as a master cylinder.The piston is forced up, lifting the car, when the high-pressure oil flows into the base of the cylinder. Closingthe oil valve keeps the piston extended until the vehicleis ready to be lowered. The air valve is opened to removethe compressed air from the oil reservoir which, in turn,reduces the oil pressure and the piston descends.

HYDRAULIC LIFT

LESSON 2


ELECTRICITY

As always, before we get to our specific focus, I willreview the basics of electricity and some generalizationsthat can be applied to electricity. Later in this lesson,we will focus on a control-wiring diagram, relays, andmotors.

Those who work with electricity must becomefamiliar with electrical codes. The National ElectricCode (NEC) is a compilation of regulations governingthe safe installation and use of electrical wiring andequipment for both residential and commercial use.In addition, local codes may stipulate more rigidrequirements than the NEC. It is mandatory that allinterior and exterior electrical wiring and electricalequipment installations adhere to both NEC and localcodes.

We will not examine electrical codes in this course,but I wanted you to be aware of their existence. Now,let’s review basics of electricity.

Electricity is the continuous flow of electrons orcurrent from one atom to another. No electron flowwill occur unless there is a pathway over which theelectrons can move. This flow is similar to a watersystem, where pipes or hoses move water from storagetanks to where it is needed. In electrical wiring, thepathway through which electrical current flows is calleda circuit. A simple circuit consists of a power source,conductors, load, and a device for controlling current.Each is described.

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• In buildings, the power source could be theelectrical generating stations that pump electricityinto residential and commercial buildings. However,other common sources of electrical power includesmall generators and batteries.

• Conductors, or wiring, provide a path for thecurrent, so it can travel from one point to another.

• A load is a device through which electricity produceswork. For example, a lamp is a load that, whenplugged in and turned on, produces light. Otherexamples of loads include heaters, electric motors,and televisions.

• Switches (on-off switches) control when electricalcurrent flows through circuits. Fuses and circuitbreakers are protective devices that control currentby preventing too much current from flowing inthe circuit, which would damage equipment. Whenan excessive amount of electricity passes throughthem, fuses and circuit breakers “blow” to stop theflow of electricity through the circuit.

In a circuit, resistance lowers the amount ofelectrical energy available to do work. Both wires andload affect resistance. It might be helpful to think of asimilar situation with a hose that is connected to twosprinklers. As water passes through a hose, turns orkinks in the pathway cause friction (which is resistance)that results in a slower flow. In addition, when some ofthe water is diverted to the first sprinkler (which is aload), less water is available for use in the secondsprinkler.

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There are two kinds of current flow. Direct currentflows in one direction. In most cases, direct current isprovided to equipment by batteries (flashlights andportable radios). Alternating current flows in onedirection, then reverses to the other direction.Alternating current is provided to equipment throughelectrical substations in buildings. In the United States,common household current reverses itself 60 times persecond. This results in 120v 60 cycle AC. Theinternational reference for cycles is defined in hertz (onehertz = 1 cycle per second).

Measurement of electric current

The rate at which electricity flows is calledamperage. It is measured in amperes. (A 100-watt bulbrequires a current of approximately 1 ampere to makeit light up completely.) Current flow is measured withan ammeter. Most electrically powered equipmentindicate the amount of current needed to operate itproperly.

Measurement of electrical pressure

Pressure is applied to electrons to force them to movethrough a conductor and around a circuit. This pressureis measured in volts. The pressure, or voltage, isavailable in wiring circuits all of the time — whetheror not electrical equipment is being used. Voltage ismeasured with a voltmeter.

Calculation of power

The amount of power derived from an electricaldevice or system is its wattage. In other words, it is theproduct obtained from electrical energy; it is the powerthat we put into use. For example, the electric companysells electrical energy.

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Electrical energy or power is measured in watts andcan be calculated as follows:

For direct-current circuits:volts × amperes = watts

For alternating-current circuits:volts × amperes × power factor = watts

NOTE: Power factors range from 0-1. Large equipment(an electric heater) may have a power factor as high as1; small equipment (a small motor) may have a powerfactor as low as .25.

Ohm’s law

Ohm’s law is a simple formula used to describe therelationship between current (flow), voltage (pressure),and resistance of an electrical circuit. Each componentinteracts to affect the operation of a circuit. In otherwords, because voltage pushes current through aresistance, a change in any of the components will resultin a change in the others. The following three equationsare Ohm’s law rearranged to solve for each of thequantities.

Current = Voltage ÷ Resistance I = E/Ramps = volts ÷ ohms An increase in voltage causes an

increase in electrical current flow. Anincrease in circuit resistance causes adecrease in electrical current flow.

Voltage = Current ××××× Resistance E = I × Rvolts = amps × ohms An increase in current causes an

increase in voltage. An increase inresistance causes an increase in voltage.

Resistance = Voltage ÷ Current R = E/Iohms = volts ÷ amps

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Tip: Make yourself a noteto memorize this

information.


GENERALIZATIONS THAT CAN BE MADE ABOUT ELECTRICITY:

• The longer the wire, the greater the resistance; the thinner the wire, the greaterthe resistance.

• An increase in temperature of a wire causes an increase in resistance.

• An ordinary electrical cord has two wires; one for flow of current from thepower source and the other for the return ground.

• The voltage (pressure) and current (flow of electricity) directly affect how muchpower is available to do work. Less energy source or lower flow will result inless electrical power being produced and vice versa.

• A series circuit has only one path for the flow of current. In a series circuit,objects are placed one after another and the current flows through each ofthem in succession. The current is the same throughout, however, and thevoltage is divided among the objects in the circuit.

• In a parallel circuit, there are 2 or more paths, or branches, for the flow ofcurrent. The current will divide and flow through each of the pathssimultaneously. Every branch has the same voltage and — if the appliances areall the same — will have the same amount of current. The total circuit resistanceis less than any one branch.

• When batteries are connected in a series, the current is the same; the totalvoltage is the sum of the voltage of each battery. The terminals are connected+, -, +, -, and so on.

• When batteries are connected in parallel, the total current is the sum of thecurrents in each battery; the total voltage is the same as that of one cell. Theterminals are connected +, +, +, and -, -, -.

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Diagnostic equipment

There are many different types of test equipmentwhich can be used to troubleshoot electrical circuits.The most common testers include light probes,voltmeters, ohmmeters, ammeters, and oscilloscopes.

A handy basic tester is called a multimeter. This is arelatively inexpensive meter that can be used to measureresistance (ohms), voltage (AC or DC), or current(amps). They are available with an analog or digitalreadout.

To familiarize you with the use of the multimeter,we will discuss the analog readout version. The digitalmeter uses the same principles.

For the discussion, refer to Diagram B whichrepresents the face of a meter.

Let’s look a little closer at the meter’s operation. Allreadings are taken using the test probes. The probesare color-coded. The black probe is for the commonground/negative connection. The red probe is for thevoltage/positive connection. The probes are insertedin the meter.

It is imperative that the leads be in the rightreceptacles. Many test readings require the correctpolarity to obtain an accurate reading. The correctpolarity is for the black probe to be placed at the morenegative point of the circuit or component being testedand the red probe placed at the more positive point.Testing a circuit with power on and with the test probepolarity reversed will result in erroneous readings andwill likely damage the meter.

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It is extremely important when making the tests onactive circuits (voltage present), that the probes are heldonly by the plastic insulators and that you do notcontact the metal tips. Serious electrical shock or deathcould result.

The face of the meter displays several scales. Thescales include ohms, DC volts, and AC volts. The scaleused is determined by the selector switch setting.

It is important to note that while the multimetertester will measure current, the capacity of these metersfor reading amperage is very low. The amperage capacityis normally in milliamps and only useful introubleshooting integrated and transistorized circuitry.Power circuits, household circuits, and the large currentapplications require an ammeter that has a largercapacity. Attempting to read a high current on astandard multimeter will damage the meter.

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Diagram B


Ohms/Resistance

Resistance, measured in ohms, is taken with thepower supply to the circuit or components turned OFF.

The first step is to place the function selector switchin the desired position. Refer to Diagram C.

Ohms/Resistance R×1 R×10 R×1K

Look at the scale labeled ohms and compare it tothe function selection. The needle reading at the levelof 5 on the scale with the selector on R×1 equals 5×1or 5 ohms. The needle reading at the level of 5 withthe selector on R×10 equals 5×10 or 50 ohms. Thesame reading with the selector on R×1K equals 5×1000or 5K ohms.

Prior to making a resistance measurement, the metermust be “zeroed.” This is accomplished by selecting thedesired meter range (R×1, etc.). The metal tips of theprobes are pressed together which creates a direct short.This means no resistance or “zero ohms.” While holdingthe tips together, the ohms adjustment is turned untilthe needle reads exactly zero ohms. Now, you are readyto make your resistance reading.

Just a couple of more tips … for the most accuratereadings, you should select the lowest possible meterrange (R1) that does not result in the meter fullydeflecting to the highest end of the scale. If the meterreads full deflection, move to the next higher scale andtry again. Also, you should make the “zero ohms”adjustment each time you change scales.

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Resistance measurements are taken by placing themeter in parallel with the measured circuit orcomponent.

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Diagram C


Voltage

The measurement of DC (direct current) and AC(alternating current) voltages are very similar. Propernegative and positive polarity are critical for DCmeasurements. In some AC applications, polarity is notimportant; however, it is a good rule to follow properpolarity rules where possible.

Step one is to select the type of voltage to be read(AC or DC) and the proper range on the functionselector. For unknown voltages, the highest rangeshould be selected. Locate the proper readout scale onthe meter and calculate the reading based on the rangeselected. If the resulting reading fits in a lower scale,move to that scale for a more accurate reading.

For voltage readings, the meter does not need to be“zeroed.”

For voltage readings, the meter is placed in parallelwith the measured circuit or component. Refer toDiagram C.

Current/Amps

Some multimeters will measure current, however,the amperage must be very low. Following the samesteps as outlined in resistance and voltagemeasurements, ensure the probes are in the propermeter receptacles. Proper polarity is critical. Select thecurrent function and desired range. Always select thehighest range first and move to lower ranges asappropriate.

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Unlike the resistance and voltage measurements,the meter must be placed in series with the test circuit.This means the circuit must be broken and the meterattached so the current will flow directly through themeter.

Ladder circuits and controls

Different electrical components have differentfunctions. Their functions and characteristics are primeconsiderations when designing circuits.

The following is a brief description of commoncomponents used in practical applications.

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Series


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Manual switches

Manual switches are devices which allow operatorscontrol of electrical circuits. Common types are directon/off switches, which can be push-button or toggleswitches. These switches remain in the position selecteduntil the operator changes them.

Momentary switches are switches that are activatedby an operator. When they are transferred, they openor close a circuit depending on the switch design andapplication for a short period of time. When theoperator releases the switch, it returns to its originalposition (starter switch on your car).

Relays

A relay is a device used to control electrical circuits.When current passes through a relay’s coils, a magneticeffect is created which mechanically transfers electricalswitches. A relay consists of normally open or normallyclosed transfer points. This means when no voltage isapplied to a relay, a circuit attached to the normallyclosed points will be active and a circuit attached tothe normally open side will not have a complete circuit.

Conversely, when the relay is energized, thenormally closed points transfer and that circuit becomesinactive. The normally open points transfer to a closedposition and activate the circuit they control.


Motors

Motors are a main component in convertingelectrical energy to work output. A basic motor has amovable armature mounted on bushings or bearings.The armature is surrounded by wire windings. As acurrent passes through the motor windings, a magneticfield is established which turns the armature. Thearmature can then be connected to pulleys or gears toprovide work output.

The size and strength of the motor is determinedby design factors which include the applied voltage,density and size of the wire windings, armature design,etc. It is important to match the application with theproper size motor.

Some motors have an overload contact built into themotor. This is a safety device to prevent damage to themotor from overheating. In an overheated condition,the overload contact will open, removing the voltagefrom the motor windings, and thus, stopping themotor. When the motor cools, the contacts willautomatically close, allowing the motor to be started.When overheating persists, the technician mustdetermine the origin of the problem.

Motors may also contain centrifugal switches. Theseare switches that transfer as the armature speeds upand are used to control both their own and othercircuits. As the motor slows down, the switchesdeactivate.

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Diagram B


With these component descriptions in mind, let’stake a look at how they could be used in a practicalcircuit. A ladder circuit is a series of circuits that dependson conditioning by another circuit in order to stepthrough their function.

Refer to Diagram B. We’ll go through the designoperation a step at a time and then do some exercises.

The intent of this circuit is to run and control threedifferent motors in a priority sequence.

The circuit is powered by 120 volts AC at 60 cycles.The emergency stop switches (ES1 and ES2) will shutoff power to the entire circuit when either of them isactivated. While the diagram shows them side-by-side,in reality, they would be placed in different locations.

The stop switch (PB1) is a momentary switchthat is normally closed. Pushing the switch will

remove voltage from the control relay (CR1).

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Start switch (PB2) is a normally open momentaryswitch, which is used to activate the entire circuit byenergizing CR1.

Step 1PB2 is depressed to start the operation. Control relay (CR1) is energized as 120volts is applied. Control relay points are transferred and points CR1-1 are closed.PB2 is released and the switch contacts open; however, the control relay remainsenergized as it is held on by the new circuit through CR1-1.

Step 2The second circuit which drives motor M1 is activated by the results of Step 1.Energizing the control relay closed relay points CR1-2. A second set of contactson PB-2 closes the circuit to M1, applying 120 volts. As M1 begins to turn, thecentrifugal switch contacts transfer. When PB2 is released, M1 continues to runas it has a new hold circuit through M1-1 and CR1-2. Circuit 1 is activated.

Step 3When motor M1 started, the centrifugal switch mechanism was activated. Thisclosed motor contact points M1-2. The closing of M1-2 applies 120 volts tomotor M2, and it begins to turn. Circuit three is activated.

Step 4When motor M2 reaches speed, the centrifugal switch in M2 was activated. Thiscloses motor contact points M2-1. The closing of M2-1 completes the circuit toapply 120 volts to M3. Circuit 4 is activated.

SummaryMotor M3 cannot run unless motor M2 is operating. Motor M2 cannot rununless motor M1 is operating. In order for M1 to run, start PB2 must be depressedand the control relay CR1 energized.

Pushing PB1 will stop the entire operation by removing voltage from the controlrelay and M1.

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EXERCISE – LADDER DIAGRAM CONTROLS

Instructions: Consider the proposed problems and answer the related questions whilecontinuing to refer to Diagram B.

1. Pushing PB2 energizes the control relay and starts M1. However,when PB2 is released, the control relay is de-energized and M1 stops.What is the likely problem?

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2. M3 will not start. What is the likely problem?

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3. On pushing start, nothing happens. While PB2 is depressed, thevoltage reading between test point 4 and X2 is 120 volts. What is thelikely problem?

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4. The system has been running fine when suddenly M2 and M3 shutdown. What is the likely problem?

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5. Nothing is running and the system cannot be started. The voltagereading between test point 2 and X2 is zero. What is the likelyproblem?

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ANSWERS TO EXERCISE

1. Pushing PB2 energizes the control relay and starts M1. However,when PB2 is released, the control relay is de-energized and M1 stops.What is the likely problem?

Answer: faulty contacts at CR1-1No hold circuit is provided for the control relay.

2. M3 will not start. What is the likely problem?

Answer: faulty motor contact at M2-1It is possible there is an overload contact at M3: however, it isunlikely as motor has not been running and is cool.

3. On pushing start, nothing happens. While PB2 is depressed, thevoltage reading between test point 4 and X2 is 120 volts. What is thelikely problem?

Answer: open coil wire on control relayThe entire applied voltage will be read across an open circuit.

4. The system has been running fine when suddenly M2 and M3 shutdown. What is the likely problem?

Answer: M2 overload contact and/or M1-2 motor contact

5. Nothing is running and the system cannot be started. The voltagereading between test point 2 and X2 is zero. What is the likelyproblem?

Answer: emergency stop switch activated or defective

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MECHANICS

Congratulations, you’ve almost made it! This is ourlast lesson in Level 6 of Applied Technology. I hope youhave progressed steadily through this level, and throughthe entire course if you have been with me from thebeginning.

As usual, I will repeat the basic concepts of machinesjust in case you need the review or if you have juststarted your study on this level. Look over them andrefresh your memory regarding these principles beforeyou start the rest of the lesson.

Hooke’s law

The greater the force exerted on an object, themore it will be moved.

For example, the heavier the weight hanging froma spring, the more the spring will be stretched.

Newton’s laws of motion

An object will remain at rest or in uniformmotion unless acted upon by an outside force.

When a force acts upon an object, it changesthe momentum of that object. This change isproportional to the applied force and to thetime that it acts upon the object.

Every action is followed by an equal andopposite reaction.

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Do you think Newton hada clue how many golferswould practice his laws?


Other generalizations about mechanics:

A machine is something that does work.

Work is done when a force causes an object to move.

Simple machines (gears, pulleys, inclined planes,levers, wheel and axle) make up compound (orcomplex) machines.

Compound machines include a bicycle, a rod andreel, a typewriter, a can opener, scissors, a hand drill, acar, a weight machine, and a treadmill.

Gears

• The force that is applied to a driver gear is trans-ferred to a driven gear.

• When two gears of different sizes are meshedtogether, the smaller gear turns faster (morerotations per minute) than the larger gear.

• Gears that are meshed together move in oppositedirections.

• The direction and speed of the driver geardetermines the speed and direction of gears thatare meshed with it.

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Pulleys

• A pulley is a wheel with a rope, belt, or chain aroundit.

• Pulleys change the direction of movement and makework easier.

• Fixed pulleys change the direction that somethingis moved; they do not make work easier.

• Movable pulleys change the direction thatsomething is moved and make work easier.

• The more pulleys in the system, the easier it is todo work (pull or lift an object).

• The more pulleys involved in a system, a greaterdistance must be pulled, but the easier it is to dowork.

• The thinner the windlass (winch), the easier it is toturn.

• In two different sets of pulleys, if the wheels areconnected by a shaft and the two wheels on onepulley are the same size as the two wheels on theother pulley, they will both turn at the same speed.

• Common pulley applications include crankshafts,sailboats, and window blinds.

Inclined Planes

• An inclined plane is a slanted surface that is used toraise or lower heavy objects from one position toanother.

• Inclined planes help reduce the amount of forceneeded to do a given amount of work, but requiregreater distance.

• The steeper the plane, the more difficult the work.• Wedges* are two back-to-back inclined planes.• Common applications of inclined planes include a

screw*, a bolt, a drill bit, a clamp, a car jack, and ascrew-on bottle top.

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*Some textbooks refer to the wedge and screw as basic simple machines.


Levers

• A lever is a bar or rod that is free to move or turnon a fulcrum.

• A lever multiplies force, but some distance must begiven up.

• The shorter the effort arm, the less force is attainedand the greater distance is attained.

• The longer the effort arm, the more force is attainedand the less distance is attained.

• Examples of levers include scissors, a broom, a clawhammer, a nutcracker, a mop, tongs, a crowbar, acan opener, tweezers, a baseball bat, boat oars, anda car jack handle.

Wheel and Axle• A wheel and axle is like a spinning lever (an ice

cream machine crank).• The center of the axle is the fulcrum.• The wheel is larger than the axle; for one rotation,

a point on the edge of the wheel travels a greaterdistance than a point on the axle. While the workdone by the axle and the wheel are the same, thegreater distance traveled of the point on the edge ofthe wheel yields a smaller force at the edge of thewheel versus the edge of the axle.

• Common wheel and axle applications include ascrewdriver, roller skates, a water-faucet handle, abicycle pedal, a can opener, and a car steering wheel.

Spatial Visualization

Spatial visualization involves the ability tomanipulate and mentally rotate two-dimensional andthree-dimensional objects. Spatial orientation involvesthe ability to perceive the elements in a pattern, tocompare patterns, and to grasp changing orientationin space.

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These types of spatial skills are highly correlatedwith the success you can achieve in a number oftechnical and professional employment situations.Spatial orientation is necessary to have a good sense ofdirection for tasks such as reading schematics, diagrams,or even maps.

Let’s review a learning activity. Have you usedspatial visualization to accomplish a task? I’ll bet youhave!

Thinking Activity

Suppose you are moving and you have to load a refrigerator, an emptydresser, and various boxes of miscellaneous items into a truck. Which wouldyou load first? Why?

Here’s what I would do. Compare your answer withmine.

I would load the refrigerator first, placing it againstthe wall near the cab of the truck. This places the weightforward of the rear axle. By placing the refrigerator inthe center of the wall, rather than against a left or rightwall, you will distribute the weight. This will preventthe vehicle from being difficult to handle.

Then, I would load the next biggest item, the emptydresser, in one of the back corners. I would fit the boxesand other miscellaneous items around the larger onesfor the best stability and least movement. Heavier boxesshould go on the opposite side of the dresser as muchas possible in order to balance the weight of the dresser.

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Do you see why visually planning how to load thetruck is better than haphazardly placing items withoutconsidering balancing the weight? You would if youhad to drive the truck on a curvy road!

OK, now that we have reviewed the basics, let’s diveinto this lesson. We will be focusing on conveyor beltswith pulleys. The principle involved will includefriction, power train (pulley system), and forcetransformers.

This type of information can be used in a widevariety of work situations and applications. Some ofthem include vibration analysis, manufacturing, drivetrains, maintenance, and frictional wearing ofmachinery.

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Effects of friction and heat

You already know about the principle of friction.When two or more objects are rubbed together, theyproduce friction, which produces heat. Sometimes thiscan be a wanted reaction, such as when starting a fireusing friction as your heat source. Also, friction isproduced when you apply brakes on your car. Thefriction or pressure on the brake shoes or pads causesthe car to come to a stop. It also produces a great dealof heat. If you have ever driven down a steep inclineor a steep mountain road, you may have noticed thatthe brakes began to smell “hot” after a while. Eventhough the brakes are still working, the heat producedby the friction begins to actually burn away the pads,causing the smell. This is not a very good condition,and depending on how hot the brakes are getting, youmay have to pull over and let them cool down beforecontinuing. This will, of course, prolong the life of yourbrake pads or shoes, as burning away the surface of thepads will cause excessive wear, which will eventuallyrequire a quicker replacement.

Friction is often an unwanted occurrence. That iswhy we keep oil in our car engines and many othermachine parts. Lubrication reduces friction; it allowssmooth movement of parts and prevents heat andburning of the part. You know what happens whenyou fail to keep your car engine’s oil sump full! Theheat produced by the constant movement of parts inthe engine will literally burn up your engine. The heatalso breaks down the oil after a certain amount of time,and the oil must be replaced. If you do not do thisperiodically, you will ruin the engine.

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You can prove this principle to yourself very easily.If you take sandpaper and sand a board, you will seethe dust particles literally fly from the board. If youuse an emery board or a nail file on your nails, you seeimmediate results with smoother nails. Also, you canprove the heat concept by sanding the board very swiftlyusing moderate pressure, and you immediately touchthe board after sanding. You will notice that it is warmto the touch.

Applications regarding this principle are commonin everyday life.

Pulley Drive Systems: Pulley systems are commonlyused. The basic idea of a pulley system is to be able tomove, lift, or do more work than a human’s strengthwould be able to do. The larger diameter pulley wouldrotate less often than the smaller diameter pulley. Youcan understand this concept by simply studying twodifferent size bicycles. The bike with the larger wheelswill turn less times to move the same distance as thebike with the smaller wheels. If you want to prove thisto yourself, you can observe two different size bicycles.Mark each bike wheel with a chalk mark. Mark a spoton the pavement at the back of the wheel. Then rollthe bike forward 360 degrees. Then, mark the pavementat the end distance. Do the same with the smaller bike.You will see that the distance traveled was less with thesmaller bike. That’s why you have to pedal twice as fastas the guy who’s on the bigger bike in order to keep upwith him! The guy who is pedaling twice as fast shouldhave to exert only half the force. Since work equalsforce times distance, the amount of work of both guysshould be the same.

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Look at the following diagrams. Determine whichwheels will rotate more.

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Bearings: Ball bearings are used to reduce frictionand heat in machine parts. A common example of thisconcept is a conveyor belt. The belt sits on top ofbearings or rollers, and the belt moves smoothly.Imagine how inefficient the conveyor would be if therewere no bearings or rollers under it. It would be literallypulled by some force to make it move. This would causeexcessive pressure on the belt and excessive heat on themain rollers on which the belt was attached. More forcewould have to be used to pull the belt; whereas, withthe belt placed on bearings or rollers, it would movemore smoothly and less force would be exerted to moveit.

Thinking Activity

Here’s a thinking question for you to consider. Why can’t you just use sometype of oil or other lubricant under the belt to effect smooth movementand use less force to move it?

Conveyor belts by necessity must be free of oilsimply because it is too messy for that purpose. Boxes,parts, or other items cannot be subjected to contactwith any lubricant or substance that would create awet, dirty, or messy part. Imagine being the person whois unloading boxes from a conveyor belt for loadingonto a delivery truck. That would be great wouldn’t it,when the boxes were covered in oil? I don’t think thatwould be tolerated well at all! Therefore, the bearingsor roller application is used instead.

Let’s think about a problem concerning pulleys andconveyor belts.

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EXERCISE – CONVEYOR BELT WITH PULLEYS

Instructions: Read the following scenario and refer to the diagram as you answer the followingquestions.

Scenario

You are a member of the maintenance department of a smallmanufacturing facility. Your responsibility is to perform routinemaintenance, troubleshoot, and solve equipment mal-functions. The plant contains many conveyor-belt systemsof various types. The conveyors transport loads of 50-100 lbloads. One particular conveyor-belt system requires anabnormally high amount of repair as compared to othersimilar systems. The problem conveyor belt, as shown in thediagram, is powered by an electric motor. (For clarity, theprotective housings are not shown.)

Maintenance personnel report a number of chronicsymptoms. It has been observed that the conveyor beltchanges speed sporadically and often moves sluggishly. Attimes, there is an odor of burnt rubber. The drive belt requiresreplacement more frequently than normal. In addition, thenoise level is abnormally high. As the motor speed increases,the noise level increases and the motor overheats.

Your job is to repair the conveyor-belt system so that it meetsnormal operating conditions. Refer to the following diagramas needed.

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Identify the Problem

1. What is your assigned task?

a. to lubricate the bearingsb. to reduce the conveyor-belt loadc. to increase the production rated. to find the causes of sluggish operatione. to check the motor speed in rpm

Define the Problem

2. What should you base your investigation upon?

a. the loadsb. symptoms reported by the maintenance personnelc. the production rated. the motor speede. the cost of the repairs

Conveyor belt

Electric motor1,760 rpm10 hp240 v AC

Conveyor feed system

Belt roller

Structural support

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Examine Alternatives

3. What subsystem is most likely responsible for the symptomsobserved?

a. electric motorb. mechanical drive system between the electric motor and the belt

rollerc. conveyor belt and rollersd. conveyor feed systeme. structural support system of the conveyor belt

4. What is the most probable cause of the system’s high maintenance?

a. The motor speed is too low.b. The belt tension is improper.c. The material load is too great.d. A drive pulley on the motor is misaligned.e. The voltage to the motor is low.

Act on a Plan

5. Considering the reported symptoms, which procedure would youperform FIRST?

a. Check the power voltage to the motor.b. Replace the drive belt.c. Lubricate the bearings.d. Replace the belt rollers.e. Check the drive-belt’s alignment.

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Look at the Result

6. You inspected the drive-belt system and found it to be misaligned.You realigned the drive-belt system. After realigning the drive beltand pulleys, what would you do to see if the problem is eliminated?

a. Restart the conveyor belt.b. Check the conveyor belt tension.c. Check the motor speed.d. Restart the conveyor belt and monitor the system’s operation.e. Estimate the production rate.

IDEAL

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ANSWERS TO EXERCISE

1. What is your assigned task?

Answer: d. to find the causes of sluggish operation

2. What should you base your investigation upon?

Answer: b. symptoms reported by the maintenance personnel

3. What subsystem is most likely responsible for the symptomsobserved?

Answer: b. mechanical drive system between the electric motor andthe belt roller

4. What is the most probable cause of the system’s high maintenance?

Answer: d. A drive pulley on the motor is misaligned.

5. Considering the reported symptoms, which procedure would youperform FIRST?

Answer: e. Check the drive-belt’s alignment.

LESSON 4


LESSON 4

6. You inspected the drive-belt system and found it to be misaligned.You realigned the drive-belt system. After realigning the drive beltand pulleys, what would you do to see if the problem is eliminated?

Answer: d. Restart the conveyor belt and monitor the system’soperation.

Are you ready to move on?


Well, that’s it. How did you do? If you had troubleor did not understand some of the concepts in thislevel, go back and review all that you need. Then takethe Posttest. I will provide the answers, as usual, at theend. But, don’t peek beforehand! That won’t help you!Good luck.

LESSON 5

No peeking!


EXERCISE – POSTTEST

Instructions: Answer the following questions about the principles of applied technology.

1. All matter is made up of particles that are in constant motion. Thismotion manifests itself as the form of energy called ____________.

2. The study of heat is called _________________________.

3. Energy can be created but not destroyed. True or False?

4. Heat requires a force to be applied to enable it to flow from hot tocold. True or False?

5. Which object will reflect heat better, a light-colored object or a dark-colored object? __________________________

6. Describe the basic operation of a car’s air-conditioning system.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

7. What is the function of the compressor?

_____________________________________________________________

_____________________________________________________________

POSTTEST


8. The part that changes the refrigerant vapor into a liquid is the___________________________.

9. The device that engages and makes the compressor run is the____________________________________.

10. Flow rate is equal to ____________________ divided by time.

11. Solve for flow rate: One gallon of water takes four minutes to flowfrom a container.

12. Fluids will flow from a place of high pressure to low pressure. Trueor False?

13. Fluid will flow along any path that is available to it. This is alsoreferred to as ____________________________________________.

14. Which container will empty faster if holes are placed at the sameheight in the containers; one has a large hole and one has a smallhole?

_____________________________________________________________

15. From which container will the stream of water be pushed thefarthest?

_____________________________________________________________

POSTTEST


16. If the holes are the same size, which container will empty faster ifone is filled with oil and one is filled with water?

_____________________________________________________________

17. Explain your answer to the previous question.

_____________________________________________________________

_____________________________________________________________

_____________________________________________________________

18. _____________________ law states that the greater the force exertedon an object the more it will be moved.

19. Give two examples where friction is a necessary force.

_____________________________________________________________

_____________________________________________________________

20. Friction always produces ___________________________.

21. What are two methods that can be used to prevent unwanted friction?

_____________________________________________________________

_____________________________________________________________

POSTTEST


22. A larger diameter pulley will rotate (less, more) often than a smallerone. (Circle the correct answer.)

23. If you have two bicycles with different size wheels, which one willtravel the least distance in one revolution?

_____________________________________________________________

24. Why are ball bearings used to reduce friction in some applications?

_____________________________________________________________

_____________________________________________________________

25. Why should you replace the oil in your car engine periodically?

_____________________________________________________________

_____________________________________________________________

26. Bernoulli’s principle states that the faster the flow of air or fluid, the(lower, higher) the pressure. (Circle the correct word.)

27. All matter is made up of particles that are in _____________________.

28. Newton’s third law of motion states that for every action there is______________________________.

POSTTEST


29. The study of heat is called:

a. hydraulicsb. thermodynamicsc. pneumatics

30. Name two devices that are components of a heating and coolingsystem.

____________________________________________________________

____________________________________________________________

31. What is the purpose of a condenser?

____________________________________________________________

32. The device used to engage the compressor in a car air-conditioningsystem is called a _________________________.

33. What is the purpose of the blower motor?

____________________________________________________________

____________________________________________________________

34. What is the purpose of the thermostat?

____________________________________________________________

____________________________________________________________

POSTTEST


35. If the pressure in a hydraulic lift remains constant, would a wideslave cylinder or a narrow slave cylinder move farther?

____________________________________________________________

36. Besides protecting from electrical overload, what is another purposeof fuses and circuit breakers?

____________________________________________________________

____________________________________________________________

37. What is the purpose of vents in a piece of equipment?

____________________________________________________________

____________________________________________________________

38. What does the fan in a computer do?

____________________________________________________________

____________________________________________________________

39. A fan moves the air around the room, but it does not actually coolthe air. True or False?

40. Heat always stays near the floor while cooler air rises to the ceiling.True or False?

41. Another term for pneumatic pressure is _______________.

POSTTEST


42. Water or oil pressure is called _________________.

43. What benefit does compressed air provide?

____________________________________________________________

____________________________________________________________

44. A water flow system has ________________________ to control anddirect the flow of water.

45. In a home water system, when you open all the faucets, what willhappen?

____________________________________________________________

____________________________________________________________

____________________________________________________________

46. Current that flows in only one direction is called:

a. alternating currentb. direct current

47. The rate at which current flows is called:

a. voltageb. amperagec. wattage

POSTTEST


48. The amount of power derived from an electrical device is:

a. voltageb. amperagec. wattage

49. Pressure is applied to electrons to force them through a conductivematerial. This pressure is measured in:

a. voltsb. ampsc. watts

50. Name at least three simple machines.

____________________________________________________________

____________________________________________________________

____________________________________________________________

51. A ________________ machine is one that is made up of more thanone simple machine.

52. Give two examples of a compound or complex machine.

____________________________________________________________

____________________________________________________________

POSTTEST


53. A ______________________ is something that does work.

54. A machine that consists of two inclined planes placed back to backis called a ____________________.

55. The center of an axle is called the:

a. leverb. hubc. fulcrum

56. How would you load a truck with the following items: piano, dresser,four chairs, assorted boxes?

____________________________________________________________

____________________________________________________________

____________________________________________________________

57. Why would positioning be important in the previous question?

____________________________________________________________

____________________________________________________________

____________________________________________________________

POSTTEST


58. ________________ ________________ involves the ability tomentally manipulate and rotate two- and three-dimensionalobjects.

59. A window blind is an example of:

a. gearb. inclined planec. pulley

60. A wood screw is an example of:

a. gearb. leverc. inclined planed. wedge

POSTTEST


ANSWERS TO EXERCISE

1. All matter is made up of particles that are in constant motion. Thismotion manifests itself as the form of energy called ____________.

Answer: heat

2. The study of heat is called ____________________.

Answer: thermodynamics

3. Energy can be created but not destroyed. True or False?

Answer: false

4. Heat requires a force to be applied to enable it to flow from hot tocold. True or False?

Answer: false

5. Which object will reflect heat better, a light-colored object or a dark-colored object?

Answer: light-colored object

6. Describe the basic operation of a car’s air-conditioning system.

Answer: It takes refrigerant from a gas stage to a liquid stage andback to a gas stage.

POSTTEST


7. What is the function of the compressor?

Answer: It pressurizes gas.

8. The part that changes the refrigerant vapor into a liquid is the___________________________.

Answer: condenser

9. The device that engages and makes the compressor run is the____________________________________.

Answer: compressor clutch

10. Flow rate is equal to ____________________ divided by time.

Answer: volume

11. Solve for flow rate: One gallon of water takes four minutes to flowfrom a container.

Answer: Qv = one quart per minute or 1/4 gallon per minute

12. Fluids will flow from a place of high pressure to low pressure. Trueor False?

Answer: true

POSTTEST


13. Fluid will flow along any path that is available to it. This is alsoreferred to as ____________________________________________.

Answer: path of least resistance/gravity

14. Which container will empty faster if the holes are placed at the sameheight in the containers; one with a large hole or one with a smallhole?

Answer: the container with the larger hole

15. From which container will the stream of water be pushed thefarthest?

Answer: the container with the smaller hole

16. If the holes are the same size, which container will empty faster ifone is filled with oil and one is filled with water?

Answer: the container with water

17. Explain your answer to the previous question.

Answer: Generally speaking, oil is of lesser density; therefore, it willflow slower allowing the container with the water to emptyfaster.

18. _____________________ law states that the greater the force exertedon an object the more it will be moved.

Answer: Hooke’s

POSTTEST


19. Give two examples where friction is a necessary force.

Answer: Answers may vary.• brakes on a car • starting a fire• tires on pavement • clutch on a car

20. Friction always produces ___________________________.

Answer: heat

21. What are two methods that can be used to prevent unwanted friction?

Answer: Answers may vary.• lubricant (oil)• ball bearings

22. A larger diameter pulley will rotate (less, more) often than a smallerone.

Answer: less

23. If you have two bicycles with different size wheels, which one willtravel the least distance in one revolution?

Answer: the one with the smaller wheels

24. Why are ball bearings used to reduce friction in some applications?

Answer: In many situations, oil is too messy and not a practical solution.

POSTTEST


25. Why should you replace the oil in your car engine periodically?

Answer: The heat from the friction in the engine will cause the oil tobreak down, making it less efficient in keeping the engineparts from overheating.

26. Bernoulli’s principle states that the faster the flow of air or fluid, the(lower, higher) the pressure.

Answer: lower

27. All matter is made up of particles that are in ________________.

Answer: constant motion

28. Newton’s third law of motion states that for every action there is______________________________.

Answer: an equal and opposite reaction

29. The study of heat is called:

Answer: b. thermodynamics

30. Name two devices that are components of a heating and coolingsystem.

Answer: Any two of the following:compressor blowershutoff valve condenserdiffusers evaporatorfilters thermostatductwork (others)

POSTTEST


31. What is the purpose of a condenser?

Answer: It changes gas (pressurizes) into a liquid.

32. The device used to engage the compressor in a car air-conditioningsystem is called a ___________________________.

Answer: compressor clutch

33. What is the purpose of the blower motor?

Answer: The blower forces the air into the ductwork.

34. What is the purpose of the thermostat?

Answer: The thermostat senses and controls the temperature.

35. If the pressure in a hydraulic lift remains constant, would a wideslave cylinder or a narrow slave cylinder move farther?

Answer: narrow slave cylinder

36. Besides protecting from electrical overload, what is another purposeof fuses and circuit breakers?

Answer: They stop the electrical current when a preset temperatureon a device is exceeded, preventing overheating of the device.This protects the individual components in the system.

POSTTEST


37. What is the purpose of vents in a piece of equipment?

Answer: ventilation, allowing air to move so that heat will notaccumulate

38. What does the fan in a computer do?

Answer: cools the components

39. A fan moves the air around the room, but it does not actually coolthe air. True or False?

Answer: true

40. Heat always stays near the floor while cooler air rises to the ceiling.True or False?

Answer: false

41. Another word for pneumatic pressure is _______________.

Answer: air pressure

42. Water or oil pressure is called _________________.

Answer: hydraulic pressure

43. What benefit does compressed air provide?

Answer: Compressed air allows a device to apply much more powerto do work.

POSTTEST


44. A water flow system has ________________________ to control anddirect the flow of water.

Answer: valves

45. In a home water system, when you open all the faucets, what willhappen?

Answer: Water pressure will be reduced at all the faucets.

46. Current that flows in only one direction is called:

Answer: b. direct current

47. The rate at which current flows is called:

Answer: b. amperage

48. The amount of power derived from an electrical device is:

Answer: c. wattage

49. Pressure is applied to electrons to force them through a conductivematerial. This pressure is measured in:

Answer: a. volts

POSTTEST


POSTTEST

50. Name at least three simple machines.

Answer: Any three of the following:wheel and axlepulleygearinclined planelever

51. A ________________ machine is one that is made up of more thanone simple machine.

Answer: compound or complex

52. Give two examples of a compound or complex machine.

Answers: Any two of the following:bicycle cartypewriter weight machinescissors can openertreadmill hand drillrod and reel (numerous others)

53. A ______________________ is something that does work.

Answer: machine

54. A machine that consists of two inclined planes placed back to backis called a ____________________.

Answer: wedge


55. The center of an axle is called the:

Answer: c. fulcrum

56. How would you load a truck with the following items: piano, dresser,four chairs, assorted boxes?

Answer: Put the piano against the center of the back wall. Put thedresser against one of the back corners. Make sure that theheavier boxes are on the opposite side as the dresser. Putchairs against the side walls and assorted boxes around theother furniture.

57. Why would positioning be important in the previous question?

Answer: The proper balance must be maintained to provide the bestequilibrium possible.

58. ________________ ________________ involves the ability tomentally manipulate and rotate two- and three-dimensionalobjects.

Answer: Spatial visualization

59. A window blind is an example of:

Answer: c. pulley

60. A wood screw is an example of:

Answer: c. inclined plane

POSTTEST


CALCULATING YOUR SCORE

Calculate your score counting the number of questions you answered correctly. If aproblem asked you to list several items or steps and you missed one or more, count thequestion as answered incorrectly. Divide the number of your correct answers by 60.Change the decimal answer to a percentage by moving the decimal two places to theright.


SUMMARY

Congratulations on yourprogress!

How well did you do on the Posttest? If you scored 90% or higher, have a reasonable chance to pass Level 6 of the Applied Technology assessment. Remember to use the IDEAL model when solving problems.

I = Identify the problemD = Define and represent the problem

boundariesE = Explore alternative approachesA = Act on a planL = Look at the result

Now, don’t be discouraged if you scored below 90%.Practice the exercises in this course – you can do it.Your enhanced work skills will pay off in the long run.Don’t forget to practice your problem-solving skills andread the Test-Taking Tips.


REFERENCE

EDWIN’S TEST–TAKING TIPS

Preparing for the test . . .

Complete appropriate levels of the WIN Instruction Solution self-study courses. Practice the exercises until you begin to feel comfortable solving problems.

Get a good night’s rest the night before the test and eat a good breakfast on test day. Your body (specifically your mind) works better when you take good care of it.

You should take the following items with you when you take the Applied Technology assessment: (1) pencils; pens are not allowed to be used on the test; it is a good idea to have more than one pencil since the test is timed and you do not want to waste time sharpening a broken pencil lead; and (2) your calculator; be sure your batteries are strong if you do not have a solar-powered calculator and that your calculator is working properly. Pencils will be provided for those who need them.

Allow adequate time to arrive at the test site. Being in a rush or arriving late will likely upset your concentration when you actually take the test.

About the test . . .

The test is comprised of approximately 32 multiple-choice questions. The questionscover four areas: thermodynamics, fluid dynamics, electricity, and mechanics. Somequestions will be presented as single questions while others may be in groups of twoand refer to specific figures or scenarios. You will not be penalized for wrong answers,so it is better to guess than leave blanks. You will have 45 minutes to complete thetest.

You will not be allowed to use scratch paper, but there is room in your assessmentbooklet to make calculations in solving.


During the test . . .

Listen to instructions carefully and read the test booklet directions. Do not hesitateto ask the administrator questions if you do not understand what to do.

Pace yourself since this is a timed test. The administrator will let you know when youhave 5 minutes left and again when you have 1 minute remaining. Work as quickly aspossible, but be especially careful as you enter numbers into your calculator.

If a problem seems too difficult when you read it, skip over it (temporarily) and moveon to an easier problem. Be sure to put your answers in the right place. Sometimesskipping problems can cause you to get on the wrong line, so be careful. You mightwant to make a mark in the margin of the test, so that you will remember to go backto any skipped problems.

Since this is a multiple-choice test, you have an advantage answering problems thatare giving you trouble. Try to eliminate any unreasonable answers and make aneducated guess from the answers you have left.

If the administrator indicates you have one minute remaining and you have someunanswered questions, be sure to fill in an answer for every problem. Your guess isbetter than no answer at all!

If you answer all of the test questions before time is called, use the extra time to checkyour answers. It is easy to hit the wrong key on a calculator or place an answer on thewrong line when you are nervous. Look to see that you have not accidentally omittedany answers.

Dealing with test anxiety . . .

Being prepared is one of the best ways to reduce test anxiety. Remember to use thefive steps that we used in solving problems: identify the problem, define the problem,explore alternatives, act on a plan, and look at the result. Identifying several ways tosolve problems and following a systematic process should increase your confidenceand reduce anxiety.

REFERENCE


Do not think negatively about the test. The story about the “little engine that could”is true. You must, “think you can, think you can, think you can.” If you prepareyourself by studying problem-solving strategies, there is no reason why you cannot besuccessful.

Do not expect yourself to know how to solve every problem. Do not expect to knowimmediately how to work the problems when you read them. Everyone has to readand reread problems when they are solving problems. So, don’t get discouraged; bepersistent.

Prior to the test, close your eyes, take several deep breaths, and think of a relaxingplace or a favorite activity. Visualize this setting for a minute or two before the test isadministered.

During the test if you find yourself tense and unable to think, try the followingrelaxation technique:

1. Put your feet on the floor.2. Grab under your chair with your hands. (Hope there are no surprises!)3. Push down with your feet and up on your chair at the same time - hold for 5

seconds.4. Relax 5 seconds (especially try to relax your neck and shoulders).5. Repeat a couple of times as needed, but do not spend the entire 45 minutes of

test trying to relax!

Studying with a partner is another way to overcome test anxiety. Encouragementfrom each other helps to increase your confidence.

REFERENCE


BASIC SCIENTIFIC PRINCIPLES

Applied Technology focuses on:• Principles related to power sources - for mechanical, electrical, thermal, and fluid

systems• Principles related to flow - for mechanical, electrical, thermal, and fluid systems• Principles related to pressure - for mechanical, electrical, thermal, and fluid systems• Principles related to resistance - for mechanical, electrical, thermal, and fluid systems

The basic scientific principles involved with energy sources, flow, pressure, and resistanceappear below:





Newton’s laws of motion• An object will remain at rest or in uniform motion unless acted upon by an outside

force.• When a force acts upon an object, it changes the momentum of that object, and

this change is proportional to the applied force and to the time that it acts uponthe object.


Laws of Thermodynamics• Energy cannot be created or destroyed.• Heat energy always flows spontaneously from hot to cold.

REFERENCE


Ohm’s law: Current is directly proportional to the voltage and inversely proportional tothe resistance.

Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally atall other points and is always at right angles to the containing surfaces.

REFERENCE

EdWIN’s Law

Mind over matter can

make people happy!


Generalizations that can be made about mechanics:

A machine is something that does work.

Work is done when a force causes an object to move.

Simple machines (gears, pulleys, inclined planes, levers, wheel and axle), which aredescribed below, make up compound (or complex) machines.

Compound machines include a bicycle, a rod and reel, a typewriter, a can opener, scissors,a hand drill, a car, a weight machine, and a treadmill.

Gears• The force that is applied to a driver gear is transferred to a driven gear.• When two gears of different sizes are meshed together, the smaller gear turns

faster (more rotations per minute) than the larger gear.• Gears that are meshed together move in opposite directions.• The direction and speed of the driver gear determines the speed and direction of

gears that are meshed with it.• Common applications of gears include bicycle sprocket chains, speedometers,

clocks, electric mixers, lawn sprinklers, and egg beaters.

Pulleys• A pulley is a wheel with a rope, belt, or chain around it.• Pulleys change the direction of movement and make work easier.• Fixed pulleys change the direction that something is moved; they do not make

work easier.• Movable pulleys change the direction that something is moved and make work

easier.• The more pulleys in the system, the easier it is to do work (pull or lift an object).• The more pulleys involved in a system, the greater distance must be pulled, but

the easier it is to do work.• The thinner the windlass (winch), the easier it is to turn.• In two different sets of pulleys, if the wheels are connected by a shaft and the two

wheels on one pulley are the same size as the two wheels on the other pulley, theywill both turn at the same speed.

• Common pulley applications include crankshafts, sailboats, boat lifts, windowblinds, cranes, elevators, and escalators.

REFERENCE


Inclined Planes• An inclined plane is a slanted surface that is used to raise or lower heavy objects

from one position to another.• Inclined planes help reduce the amount of force needed to do a given amount of

work, but require greater distance.• The steeper the plane, the more difficult the work.• Wedges are two back-to-back inclined planes.• Common applications of inclined planes include a screw, a bolt, a drill bit, a

clamp, a car jack, and a screw-on bottle top.

Levers• A lever is a bar or rod that is free to move or turn on a fulcrum.• A lever multiplies force, but some distance must be given up.• The shorter the effort arm, the less force is attained and the greater distance is

attained.• The longer the effort arm, the more force is attained and the less distance is attained.• Examples of levers include scissors, a broom, a claw hammer, a nutcracker, a mop,

tongs, a crowbar, a can opener, tweezers, a baseball bat, boat oars, and a car jackhandle.

Wheel and Axle• A wheel and axle is like a spinning lever (an ice cream machine crank).• The center of the axle is the fulcrum.• The wheel is larger than the axle; for one rotation, a point on the edge of the

wheel travels a greater distance than a point on the axle. While the work doneby the axle and the wheel are the same, the greater distance traveled of thepoint on the edge of the wheel yields a smaller force at the edge of the wheelversus the edge of the axle.

• Common wheel and axle applications include a screwdriver, roller skates,a water-faucet handle, a bicycle pedal, a can opener, and a car steering wheel.

REFERENCE


Overview of Electricity

Electricity is the continuous flow of electrons, or current, from one atom to another. Noelectron flow will occur unless there is a pathway over which the electrons can move.This flow is similar to a water system, where pipes or hoses move water from storagetanks to where it is needed. In electrical wiring, the pathway through which electricalcurrent flows is called a circuit. A simple circuit consists of a power source, conductors,load, and a device for controlling current. Each is described below.

In buildings, the power source could be the electrical generating stations that pumpelectricity into residential and commercial buildings. However, other common sourcesof electrical power include small generators and batteries.

Conductors, or wiring, provide a path for the current so that it can travel from one pointto another.

A load is a device through which electricity produces work. For example, a lamp is a loadthat, when plugged in and turned on, produces light. Other examples of loads includeheaters, electric motors, and televisions.

Switches (on-off switches) control when electrical current flows through circuits. Fusesand circuit breakers are protective devices that control current by preventing too muchcurrent from flowing in the circuit, which would damage equipment. When an excessiveamount of electricity passes through them, fuses and circuit breakers “blow” to stop theflow of electricity through the circuit.

In a circuit, resistance lowers the amount of electrical energy available to do work. Bothwires and load affect resistance. It might be helpful to think of a similar situation with ahose that is connected to two sprinklers. As water passes through a hose, turns or kinksin the pathway cause friction (which is resistance) that results in a slower flow. In addition,when some of the water is diverted to the first sprinkler (which is a load), less water isavailable for use in the second sprinkler.

REFERENCE


There are two ways or methods of having current flow. Direct current flows in onedirection. In most cases, direct current is provided to equipment by batteries (flashlightsand portable radios). Alternating current flows in one direction, then reverses to theother direction. Alternating current is provided to equipment through electrical substationsin buildings. In the United States, common household current reverses itself 60 timesper second. This results in 120v 60 cycle AC. The international reference for cycles isdefined in hertz (one hertz = 1 cycle per second).

Measurement of Electric Current

The rate at which electricity flows is called amperage. It is measured in amperes. A 100-watt bulb requires a current of approximately 1 ampere to make it light up completely.Current flow is measured with an ammeter. Most electrically powered equipment indicatethe amount of current needed to operate it properly.

Measurement of Electrical Pressure

Pressure is applied to electrons to force them to move through a conductor and around acircuit. This pressure is measured in volts. The pressure, or voltage, is available in wiringcircuits all of the time - whether or not electrical equipment is being used. Voltage ismeasured with a voltmeter.

Calculation of Power

The amount of power derived from an electrical device or system is its wattage. In otherwords, it is the product obtained from electrical energy; it is the power that we put intouse. For example, the electric company sells electrical energy. Electrical energy or poweris measured in watts and can be calculated as follows:

For direct-current circuits: volts ××××× amperes = watts

For alternating-current circuits: volts ××××× amperes ××××× power factor = watts

NOTE: Power factors range from 0-1. Large equipment (an electric heater) may have apower factor as high as 1; small equipment (a small motor) may have a power factor aslow as .25.

REFERENCE


Ohm’s law

Ohm’s law is a simple formula used to describe the relationship between current (flow),voltage (pressure), and resistance of an electrical circuit. Each component interacts toaffect the operation of a circuit. In other words, because voltage pushes current througha resistance, a change in any of the components will result in a change in the others. Thefollowing three equations are Ohm’s law rearranged to solve for each of the quantities:

Current = Voltage ÷ Resistance I = E/Ramps = volts ÷ ohms An increase in voltage causes an increase in

electrical current flow. An increase in circuitresistance causes a decrease in electrical currentflow.

Voltage = Current ××××× Resistance E = I ××××× Rvolts = amps × ohms An increase in current causes an increase in

voltage. An increase in resistance causes anincrease in voltage.

Resistance = Voltage ÷ Current R = E/Iohms = volts ÷ amps

REFERENCE


Generalizations that can be made about electricity:

• The longer the wire, the greater the resistance; the thinner the wire, the greaterthe resistance.

• An increase in temperature of a wire causes an increase in resistance.

• An ordinary electrical cord has two wires; one for the flow of current from thepower source and the other for the return or ground.

• The voltage (pressure) and current (flow of electricity) directly affect how muchpower is available to do work. Less energy source or lower flow will result in lesselectrical power being produced.

• A series circuit has only one path for the flow of current. In a series circuit, objectsare placed one after another and the current flows through each of them insuccession. The current is the same throughout, however, and the voltage is dividedamong the objects in the circuit.

• In a parallel circuit, there are 2 or more paths, or branches, for the flow of current.The current will divide and flow through each of the paths simultaneously. Everybranch has the same voltage and - if the appliances are all the same - will have thesame amount of current. The total circuit resistance is less than any one branch.

• When batteries are connected in a series, the current is the same; the total voltageis the sum of the voltage of each battery. The terminals are connected +, -, +, -,and so on.

• When batteries are connected in parallel, the total current is the sum of the currentsin each battery; the total voltage is the same as that of one cell. The terminals areconnected +, +, +, and -, -, -.

REFERENCE


Generalizations that can be made about heat:

• Heat travels through conductors (e.g., metal) better than through insulators (e.g.,wood).

• Dark-colored surfaces absorb more heat than light-colored surfaces.

• Rough or dull surfaces absorb more heat than smooth or shiny surfaces.

• When friction causes heat, the object that is in constant contact gets hotter thanthe movable object. (For example, the wood being cut gets hotter than the sawblade; car brake shoes get hotter than the wheel).

Generalizations that can be made about fluids:

Pressure• The amount of pressure exerted by a fluid depends upon the height and the density

of that fluid and is independent of the shape of the container that is holding thefluid.

• The deeper the fluid, the greater the pressure it exerts.

• The denser the fluid, the greater the pressure it exerts (salt water is denser thanfresh water).

• Fluids seek equilibrium - they seek their own level; a fluid will flow from a place ofhigh pressure to a place of low pressure.

• A fluid can never rise higher than its source without an external force (a pump).

REFERENCE


Evaporation• The higher a liquid’s temperature, the faster it will evaporate.

• The lower a liquid’s pressure, the faster the liquid will evaporate.

• The more area of liquid that is exposed to air, the faster the liquid will evaporate.

• The more circulation of air above a liquid, the faster the liquid will evaporate.

Boiling Point• Increased pressure on a liquid raises the liquid’s boiling point.

• Decreased pressure on a liquid lowers the liquid’s boiling point.

REFERENCE


BIBLIOGRAPHY

Adkinson, S., & Fleer, M. (Eds.). (1995). Science with reason. London: Hodder andStoughton Educational.

American Association for the Advancement of Science (1993). Benchmarks for scienceliteracy: A project 2061 report. New York: Oxford University Press.

American Association for the Advancement of Science (1990). Science for all Americans:A project 2061 report on literacy goals in science, mathematics, and technology. New York:Oxford University Press.

Bransford, J., & Stein, B. (1984). The IDEAL problem solver: A guide for improvingthinking, learning, and creativity. New York: W. H. Freeman and Co.

Ohio Department of Education (1994). Ohio’s competency-based science model: Scientificliteracy for the 21st century. Columbus, OH: State Board of Education.

National Council of Teachers of Mathematics (1993). Curriculum and evaluationstandards for school mathematics. Reston, VA: NCTM.

National Research Council (1996). National science educational standards. Washington,DC: National Academy Press.

The Secretary’s Commission on Achieving Necessary Skills (1992). Learning a living:A blueprint for high performance: A SCANS report for America 2000. Washington, DC:U.S. Department of Labor.

REFERENCE


ANSWERS TO POP QUIZ QUESTIONS

Page 28 — Compressor – a device that pressurizes gases

Page 30 — IDEAL Strategy• Identify the problem• Define and represent that problem• Explore alternatives• Act on a plan• Look at the result

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