INTRODUCTION TO CURRENT ELECTRICITY

It’ll Move You!!

TYPES OF ELECTRICITY We know there are 2 types of electricity:

1. Static Electricity – where electrons build up an electric charge on a substance by friction, contact, or induction. These electrons do NOT travel in a wire.

Not useful for operating electrical devices because they do not flow continuously.

2. Current Electricity – where an electric charge moves from a source of electrical energy along a wire in an electric current.

The electrons must have a complete path, or circuit to flow through to flow continuously.

SOURCES OF ELECTRICAL ENERGY: ELECTROCHEMICAL CELLS This is a package of chemicals that

converts chemical energy into electrical energy that is stored in charged particles.A simple one includes an electrolyte and

two electrodes. Electrolyte: liquid/paste that conducts

electricity because its chemicals form ions. e.g.: citric acid

Electrode: metal strips, usually one each of zinc and copper, that react with the electrolyte.Zinc becomes negative, copper becomes

positiveA battery is a combination of

electrochemical cells.

TYPES OF ELECTROCHEMICAL CELLS Wet Cell

An electrochemical cell that has a liquid electrolyte.

Often used for vehicles. Dry Cell

An electrochemical cell that has a paste electrolyte.

Often used in flashlights, PSPs, cameras, watches, etc.

Fuel CellAn electrochemical cell that generates

electricity directly from a chemical reaction with a fuel that is continuously added.

RECYCLING AND RECHARGING: DRY CELLS Eventually the chemicals in a dry cell are

used up and can no longer separate the charges onto the metal strips.

Over 50% of heavy metals (nickel, cadmium, lead) found in landfills are caused by household dry cells and batteries.

Recharging batteries reverses the chemical reactions in a cell and restores the reactants that are used up when the cell produces electricity.Since they can be reused many times, this means

there is less impact on the environment --

QUICK LAB Purpose: to discover how to make

flashlight bulbs light up using a standard battery.

Materials: 1D dry cell, 5 insulated copper wires with both ends bare, 2 2.0V-flashlight bulbs

QUICK LAB CONTINUED... (~10MINUTES) Procedure:

1. Use wire and the dry cell to make one bulb light up. Record/draw your arrangement.

2. Use wire and the dry cell to make two bulbs light up. Record/draw your arrangement.

3. If time allows, try other arrangements for step 1 and step 2.

QUESTIONS ON THE QUICK LAB:TO HAND IN (~5 MINUTES)

The tallest person in your group will record your answers to the following questions, while the shortest person will read them out to the class. The middle person will need to know how to draw a diagram on the board if asked.

1. Explain how to use wire and a dry cell to make one bulb light up. Include a labelled sketch in your answer.

2. Explain how to use wire and a dry cell to make two bulbs light up. Include a labelled sketch in your answer.

ANSWERS TO LAB QUESTIONS Out of 57 or 38, depending on the class

you’re in If it’s out of 38, I didn’t count the Part C

Steps 3 and 4 observations or Question 5b on the Analysis

ANSWERS TO LAB QUESTIONSPart A:

Procedure Observation (Describe what happens)

1. Rub an ebonite rod with a piece of fur.

2. Bring the ebonite rod near some paper confetti.

attracts the confetti

1. Bring the fur near some confetti.attracts the confetti

ANSWERS TO LAB QUESTIONS Part B:

Procedure Observation (Describe what happens)

1. Blow up 2 balloons2. Rub (for several seconds) each

balloon with your hair or the fur.

3. After rubbing, bring the balloon face close to your own. What happens? Have a partner watch.

small shocktingly feeling

balloon is sticking to your face

1. Hold the balloon faces slightly apart. What happens? they repel

1. Bring the fur that you rubbed against the balloon close to it. What happens?

fur is attracted to balloon

1. Bring the balloon close to some confetti. What happens?

confetti is attracted to balloon

ANSWERS TO LAB QUESTIONS Part C:

Procedure Observation (Describe what happens)

1. Rub an ebonite rod with fur and bring it close to, but NOT TOUCHING the hanging pith ball. What happens?

2. Then, touch the pith ball with the rod. What happens?Neutralize the pit ball by touching it.

1. Pith ball is attracted to ebonite rod

2. Pith ball is attracted to rod, then acquires the same charge and is repelled

1. Rub an acetate strip with a silk strip and bring it close to, but NOT TOUCHING the hanging pith ball. What happens?

2. Then, touch the pith ball with the rod. What happens?Neutralize the pith ball by touching it.

3. Pith ball is attracted to acetate strip

4. Pith ball is attracted to strip, then acquires the same charge and is repelled

ANSWERS TO LAB QUESTIONS1. Describe the behaviour of uncharged

objects placed near charged objects. (1 mark)Uncharged objects are attracted to charged objects.

Why do they behave this way if they are not charged? (1 mark)|The Law of Electric Charges states it’s so.

ANSWERS TO LAB QUESTIONS1. Does the force of attraction between

charged and uncharged objects get stronger or weaker as the distance between them increases? Explain using an example from this investigation.(3 marks)Force of attraction weakens as distance increases; for example, as you move the negatively charged ebonite rod away from the neutral pith ball, the pith ball is less and less attracted to the ebonite rod.

ANSWERS TO LAB QUESTIONS Based on your observations, describe

the behaviour of objects brought close to one another:When they have like charges

(2 marks)Like charges repel.

When they have unlike charges(2 marks)

Unlike charges attract.

ANSWERS TO LAB QUESTIONS

What test could you perform to determine:Whether an object is charged or uncharged? (2

marks)Bring a neutral object near the object in question; nothing will happen if it’s not charged; if the object is charged, the neutral object will be attracted to the object in question.

The kind of charge present on a charged object?(2 marks)

Bring a charged object (whose charge you know) towards the unknown object and see if they attract or repel; if they attract, they have opposing charges; if they repel, they have the same charge.

QUESTION #5 ON THE BOARD Please look at the blackboard.

ELECTRIC CIRCUITS An electric circuit controls the flow of electric

current. There are four parts in a simple electric circuit:

1. A source of electric energy which supplies the current.

2. An electric load to convert electrical energy to a different type of energy.

3. A control switch to control the flow of electric current.

4. A connector or conductor to connect all parts of the circuit together.

Use the labels given to you to label 3 of the 4 parts of the circuit.

PARTS OF AN ELECTRIC CIRCUIT In the circuit we made in the Quick Lab,

which parts correspond to the:Source?

BatteryControl switch?

Nothing!! Conductor?

WiresLoad?

Light bulb

CHECKPOINT! TRY NOT TO USE YOUR NOTES!! 1. How is current electricity different from

static electricity?2. What is an electric circuit?3. List three components of an electric

circuit.4. What is the difference between an

electrolyte and an electrode?5. Why should dry cells be recycled

rather than thrown in the trash?

MATCH IT UP! You and your partner (who’s sitting

beside you) will be using your noggins to match up each electric circuit to its corresponding description.

You have about 10 minutes to complete this task.

We will then take this up as a class!!

ANSWERS TO ‘MATCH IT UP’

1 – c 2 – g 3 – e 4 – d 5 – f 6 – h 7 – b 8 – i 9 – a

USE THAT ACQUIRED KNOWLEDGE!

Now, take that knowledge you gleaned from the previous activity and extend it to fill out your Electrical Symbols sheet with drawings of the symbols of each of the components of an electric circuit.

SOME KEY DEFINITIONS Switch – Fuse – Circuit breaker – Load – Resistor – Ammeter – Voltmeter –

ELECTRICAL SYMBOLS ANSWERS

THE RULES:DRAWING CIRCUIT DIAGRAMS Circuit diagram – drawing made with

symbols that shows the components and connections in a circuit

You MUST remember the following TIPS when creating your circuit diagrams:1. Always use a ruler to draw straight lines

for the conducting wires.2. Make right-angle corners so that your

finished diagram is a rectangle.

LAB:DRAWING CIRCUIT DIAGRAMS Using the correct electrical symbols,

draw the electric circuit that you see at each of the 6 workstations.

REMEMBER TO USE THE RULES!!!!!!!!!!!!!