Questions: 1.Where does electricity come from? 2.What are the sources of electricity? 3.Do I know how to connect bulb(s) to battery/batteries correctly?

Presentation on theme: "Questions: 1.Where does electricity come from? 2.What are the sources of electricity? 3.Do I know how to connect bulb(s) to battery/batteries correctly?"— Presentation transcript:

Questions: 1.Where does electricity come from? 2.What are the sources of electricity? 3.Do I know how to connect bulb(s) to battery/batteries correctly? 4.Do I know the symbols for each of the electrical components? ELECTRICAL SYSTEM

5. What is a series circuit? 6. What is a parallel circuit? 7. Do I know how to draw a circuit diagram accurately? 8. Am I able to observe & compare different circuits and identify the variables changed? 9. 9. What affects the brightness or current flowing through a bulb? ELECTRICAL 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 SYSTEM

The Electric Bulb

Series / Parallel?

Compare

What Affects the Brightness / Current Flowing through a Bulb? More batteries  Higher current  Brighter bulb What kind of arrangement? Batteries arranged in series.

What Affects the Brightness / Current Flowing through a Bulb? More bulbs  Lower current  Dimmer bulbs What kind of arrangement? Bulbs arranged in series.

What Affects the Brightness / Current Flowing through a Bulb? More bulbs  Same current  Same brightness of bulbs What kind of arrangement? Bulbs arranged in parallel.

Is it true… … the second bulb is less bright than the first bulb in a series circuit because electric current has been ‘used up’ by the first bulb in the circuit? … the second bulb is less bright than the first bulb in a series circuit because electric current has been ‘used up’ by the first bulb in the circuit? … in an open circuit, electric current flows to the part where there is a gap and ‘turns back’ to the battery as it cannot flow across the gap? … in an open circuit, electric current flows to the part where there is a gap and ‘turns back’ to the battery as it cannot flow across the 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 & C Answer: 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

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