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# S3 Physics -

Magnetism and Electricity (II). S3 Physics -. 1. 2. 3. 4. 5. 6. 7. 10. 11. 12. 13. 14. 8. 9. 15. 16. 17. 18. 19. 20. 21. answer. What do you use to measure current and how do you place it in a circuit?. Use an ammeter. Place it in series. answer.

## S3 Physics -

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1. Magnetism and Electricity (II) S3 Physics - 1 2 3 4 5 6 7 10 11 12 13 14 8 9 15 16 17 18 19 20 21

2. answer • What do you use to measure current and how do you place it in a circuit? Use an ammeter. Place it in series.

3. answer 2. What do you use to measure voltage and how do you place it in a circuit? Use a voltmeter. Place it in parallel.

4. answer 3. How is resistance related to current? As the resistance increases… the current decreases.

5. answer 4. What is the unit of resistance? Ohms (Ω)

6. answer 5. What could you use to alter the current in a circuit? Give an application. A variable resistor. This is used in dimmer switches, volume controls etc…

7. answer 6. What happens to electrical energy when there is resistance in a wire? The electrical energy is converted to heat energy.

8. answer 7. Give an example of where we use electrical energy being converted to heat energy. A kettle, toaster, electrical heater.

9. answer 8. How does a thermistor work? Its resistance varies with temperature

10. answer 9. What type of resistor might be controlled using e.g. sunlight? A light dependant resistor

11. answer What is electrical power? The rate at which electrical energy is converted into other forms.

12. answer 11. How does a switch control a series circuit? All switches must be closed in order for a a series circuit to operate.

13. answer 12. What’s the difference between a series and a parallel circuit? Series circuits have one path, parallel circuits have parallel branches.

14. answer 13. What is observed when a metal object is brought close to a charged Van de Graaf dome? Explain why? A spark. The Van de Graaf dome is positively charged. Negative charge moves from the metal object to the dome through the electric field.

15. answer 14. Match the correct fuse to each appliance. (3, 7 or 13 A) 13A 3A 7A

16. answer 15. How does an earth wire work? By providing an easy path for electricity to flow to ground.

17. answer 16. Why do plastic cased appliances not require an earth wire? Because they are DOUBLE INSULATED. This means that there is no risk of electrocution from the casing.

18. answer 17. Why are household circuits in parallel? This means that each appliance receives the full voltage AND that other appliances remain on when you switch one off.

19. answer 18. What is a ring circuit? Why is it an advantage to use in a house? It is a parallel circuit with more than one path to each socket. Thinner cables can be used since there is less current.

20. answer 19. How does a mains fuse work? What is the difference between a mains fuse and a circuit breaker? A mains fuse protects the mains wiring by breaking if too large a current is drawn. A breaker is an automatic switch which will trigger when too large a current is drawn. Breakers can be reset and used again.

21. answer 20. How is an electromagnet turned into a magnet? By flowing a current through the coil

22. answer 21. How does a fuse act as a safety device? It melts if the current is too high.

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