ELECTRICAL SYSTEM

Questions:Questions:1.1. Where does electricity come from?Where does electricity come from?2.2. What are the sources of electricity?What are the sources of electricity?3.3. Do I know how to connect bulb(s) to Do I know how to connect bulb(s) to

battery/batteries correctly?battery/batteries correctly?4.4. Do I know the symbols for each of the Do I know the symbols for each of the

electrical components?electrical components?

ELECTRICAL SYSTEMELECTRICAL SYSTEM

5. What is a series circuit?5. What is a series circuit?6. What is a parallel circuit?6. What is a parallel circuit?7. Do I know how to draw a circuit diagram 7. Do I know how to draw a circuit diagram

accurately?accurately?8. Am I able to observe & compare different 8. Am I able to observe & compare different

circuits and identify the variables changed?circuits and identify the variables changed?9. 9. What affects the brightness or current

flowing through a bulb?

ELECTRICAL SYSTEMELECTRICAL SYSTEM

10. What are electrical conductors and insulators?

11. Do I know how to use electricity safely?12. What are some ways to conserve

electricity?

ELECTRICAL SYSTEMELECTRICAL SYSTEM

The Electric BulbThe Electric Bulb

Series / Parallel? Series / Parallel?

Series / Parallel?Series / Parallel?

CompareCompare

What Affects the Brightness What Affects the Brightness / Current Flowing through a / Current Flowing through a

Bulb?Bulb?More batteries More batteries Higher current Higher current Brighter bulb Brighter bulb

What kind of arrangement?What kind of arrangement?

Batteries arranged in series.

What Affects the Brightness What Affects the Brightness / Current Flowing through a / Current Flowing through a

Bulb?Bulb?More bulbs More bulbs Lower current Lower current Dimmer Dimmer bulbsbulbs

What kind of arrangement?What kind of arrangement?

Bulbs arranged in series.

What Affects the Brightness What Affects the Brightness / Current Flowing through a / Current Flowing through a

Bulb?Bulb?More bulbs More bulbs Same current Same current Same brightness of bulbs Same brightness of bulbs

What kind of arrangement?What kind of arrangement?

Bulbs arranged in parallel.

Is it true…Is it true…

• … … the second bulb is less bright than the first the second bulb is less bright than the first bulb in a series circuit because electric bulb in a series circuit because electric current has been ‘used up’ by the first bulb in current has been ‘used up’ by the first bulb in the circuit?the circuit?

• … … in an open circuit, electric current flows to in an open circuit, electric current flows to the part where there is a gap and ‘turns back’ the part where there is a gap and ‘turns back’ to the battery as it cannot flow across the to the battery as it cannot flow across the gap?gap?

1. The diagram below shows a circuit and what happens to the lamp when three rods, A, B and C are placed, one at a time, across PQ.

From the results, which rod is most likely to be a conductor of electricity? Give a reason. (1m)

Key Word(s): conductor of electricity, reason

Answer: Rod B. As the bulb lights up, this means that Rod B allows electricity to pass through it, forming a closed circuit.

In another experiment, some wax was placed on the top end of the same three rods, A, B and C. The three rods were then placed on top of a hot surface as shown below. It was observed that the wax on rod B melted first, followed by that on rod C and then rod A.(b) What conclusion can you draw about the conduction of heat in rods A, B and C? (1m)

Key Word(s): conduction of heat in A, B & CAnswer: Rod B conducts heat the fastest,

followed by rod C and finally rod A.

(c) From your answers to (a) and (b), what can

you conclude about the likely relationship

between a conductor of electricity and a

conductor of heat? (1m)

Key Word(s): *relationship between

conductor of electricity & conductor of heat

(*relationship: Order is important)

Answer: A material which is a conductor of

electricity is also a good conductor of heat.

2. (a) In the circuits P and Q below, all the bulbs are lit.

In the table below, write down the number of bulbs that would remain lit when one of the bulbs in each circuit is blown.

Key Word(s): number of bulbs, remain lit, one bulb is blown

Skill(s): Observe & Compare the circuits

Variable changed: Arrangement of bulbs

Answer: Circuit P – 3, Circuit Q - 2

(b) In circuit R below, all the bulbs B1, B2, B3 and B4 are lit.

Write down the smallest number and the largest number of bulbs that would remain lit when one of the bulbs in circuit R is blown.

Give a reason for your answer. (2m) Highlight key word(s). Highlight paths of electric current. (i) Smallest number of bulbs remaining lit: 0 Reason: When bulb B1 or B4 is blown, the

circuit is open.

(ii) Largest number of bulbs remaining lit: 3 Reason: When B2 or B3 is blown, electricity

can still pass through another path, there will still be a closed circuit.

3. Samy set up an experiment as shown below.

When the metal clips were connected to the container, the bulb lit up.

State whether liquid P and material Q must be conductor(s) of electricity.

Give a reason for your answer. Skill(s): Observe the diagram Highlight key word(s) in the question & on the diagram. Key Concepts: close / open circuit

3. Samy set up an experiment as shown below.

When the metal clips were connected to the container, the bulb lit up.

State whether liquid P and material Q must be conductor(s) of electricity.

Give a reason for your answer.

Answer: Liquid P – No. The metal clips are not connected to liquid P. The electricity does not need to pass through liquid P.

Material Q – Yes. The metal clips are connected to material Q, so it must be a conductor of electricity to close the circuit / to allow electricity to pass through it.

4 (a) Andrea wants a light bulb to light up when her toy train is pushed through a tunnel. She makes an electric circuit for her toy train. Andrea makes a tunnel and puts a strip of foil inside the tunnel roof. The picture shows Andrea’s tunnel and the wiring on her train.

The foil strips on the train act like a switch.

When both foil strips on the train touch the

foil inside the tunnel roof, the bulb lights up.

Complete the circuit diagram below by

drawing the switch and the bulb to show

the circuit on Andrea’s train. (2m)

Give ONE property of metal foil which makes it

a good material for Andrea to use as a switch. (1m)

It is an electrical conductor. / It is flexible.

When only one foil strip on the train is touching

the foil in the tunnel, the bulb does not light

up.Complete the sentence to explain why the

bulb does not light up. (1m)

The circuit is open. / The circuit is not closed.

(d) The bulb on the train only lights up when all of the train is inside the tunnel. Andrea wants to improve her circuit so the bulb lights up when the train has only just entered the tunnel.

Which train has foil strips that would allow the bulb to light up when the train has only just entered the tunnel? (1m)

Answer: Top right