Current ElectricityIntroductory Physics

Canadian Academy

Group Members

V

Current Electricity Construct and explain

Work in pairs or by yourself for these tasks With each question

bull Build it in the PhET simulationbull Build it in the lab if possiblebull Draw the circuit diagram and

answer the questions on the slide

httpphetcoloradoeduensimulationcircuit-construction-kit-dc

You should be able tobull Define current electricitybull Define resistance and state the factors that

affect resistance in a metal wirebull Define potential difference (voltage)bull Explain the effect of potential difference

and resistance on a currentbull Draw basic circuit diagrams involving

batteries lamps switches and wiresbull Define electrical power including the

relationship to voltage and current

Your finished work should be uploaded to SlideShare (or

Google Docs if it works) and embedded into a blog post

+ - + -

cell batterywire

junction

bulb lamp

cathode anode

switch

resistor

V A

voltmeter ammeter

Some basic circuit symbolsYou can use these to build the circuits on the next slides

What do these two components measure

electron flow

conventional current

A simple series circuitBuild this circuit

Define current electricity bull

Label the direction of flow of electrons and the direction of the conventional current What is the difference between them

Use the non-contact ammeter to measure the current in the circuit

bull

What happens if the cell is not included in the circuit Explain

bull

A

Switches and currentBuild this circuit

Measure the current with the switch in the open position

bull

Close the switch and measure the current Explain your answer

bull

Move the ammeter to different positions in the circuit and measure the current Does position matter

bull

Are electrons lsquoused uprsquo in the circuit Are electrons lsquocreatedrsquo in the cell

A

Potential Difference (voltage)Modify the circuit to increase the potential difference by including two then three cells

What happens to the bulb bull

Measure the current and potential difference

Complete the circuit diagram for three cells

A

V

Define potential difference (voltage) bull

Explain your results bull

Cells Current (A) Potential Difference (V)

1

2

3

Resistance (incandescent bulbs or lamps)Go to the following applet and see resistance at a molecular level and how a light bulb workshttpmicromagnetfsueduelectromagjavafilamentresistance

Explain in your own words how moving charges cause a bulb to glow What energy transfers and transformations are taking place

Explain what has happened when a cell (battery) has run out

Resistance (incandescent bulbs or lamps)Build this circuit Add bulbs and record your observations

Bulbs Current (A) Observations

1

2

3

4

5

Explain your findings in detail

Remove all the bulbs to create a short circuit and measure the current Explain

A

Conclusions Use your findings in the circuits so far to write your own Laws

Law of current in a loopldquo ldquo

Law of voltage and current (whatrsquos the relationship)

ldquo ldquo

Law of resistance and current (whatrsquos the relationship)

ldquo ldquo

Why is it dangerous to have too little resistance in a circuit

10

=VR

A

VΩ

I

Arrange this equation based on your own observations

current

potential difference

resistance

11

= VRcurrent

potential difference

resistance

A

V

Ω

IArrange this equation based on your own observations

Parallel Circuits How many different routes can current take through this circuit

bull

Close the lower switch only Observe the bulb and measure the current

bull

Close the upper switch only Observe the bulb and measure the current

bull

Close both switches Observe the bulbs and measure the current at different positions

Observe the animation carefully What happens to the electrons at junctions

Draw a circuit diagram for this set-up below

11

= VRcurrent

potential difference

resistance

A

V

Ω

IArrange this equation based on your own observations

Parallel Circuits How many different routes can current take through this circuit

bull

Close the lower switch only Observe the bulb and measure the current

bull

Close the upper switch only Observe the bulb and measure the current

bull

Close both switches Observe the bulbs and measure the current at different positions

Observe the animation carefully What happens to the electrons at junctions

Draw a circuit diagram for this set-up below

Parallel Circuits How many different routes can current take through this circuit

bull

Close the lower switch only Observe the bulb and measure the current

bull

Close the upper switch only Observe the bulb and measure the current

bull

Close both switches Observe the bulbs and measure the current at different positions

Observe the animation carefully What happens to the electrons at junctions

Draw a circuit diagram for this set-up below

Law of Parallel Circuits

Law of parallel circuitsldquo ldquo

Write your own Law based on observations

Now test your Law using a third bulb in parallel Draw the circuit diagram below and write your observations of the bulbs and of current

More Parallel CircuitsClose one switch at a time and record your observations

bull

Close both switches and record your observations bull

Carefully observe the junctions What is happening Explain with reference to resistance and junctions

bull

Do you need to modify your Law of Parallel Circuits

Draw a circuit diagram for this set-up below

Law of Parallel Circuits

Law of parallel circuitsldquo ldquo

Modify your Law

More ResistanceUse two cells and two bulbs in a circuit Use CTRL-click to adjust the resistance of the bulbs (one is 20 ohms (Ω) the other is 10Ω)

What is the difference between these two bulbs on a molecular levelbull

Wire up the bulbs in two different circuits series and parallel Draw the circuits below Under each circuit record and explain your observations

Series Parallel

Electrical PowerDefine electrical power and state its unit bull

What is the relationship between electrical power and lsquopowerrsquo as we have studied in the previous unit

bull

Compare two methods of generating electrical power one fossil-fuel based and one renewable How do they work What are the benefits disadvantages of each

ExtensionIf you finish with extra time

bull Check the Laws you have written against published information Do they concurbull Find out more about circuits and their components bull Find out about the difference between AC and DC bull Build your own circuits and draw the circuit diagrams below

For more resources

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