# IGCSE Electricity

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 Author: SilcoatesScience ID: 300259 Filename: IGCSE Electricity Updated: 2015-04-08 11:15:52 Tags: IGCSE Electricity Folders: Description: IGCSE Electricity Show Answers:

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1. What name is given to current that only flows in one direction?
Direct current (dc)
2. What sort of current is supplied by cells and batteries?
Direct current (dc)
3. What do the letters a.c. represent?
Alternating current
4. What is the period of an ac wave?
• The time for a complete cycle
5. What is the relationship between the frequency (f) and the time period (T) of an ac wave?

(T in seconds, f in Hz)
6. What names are given to the three wires in a UK mains plug?
• Live
• Neutral
• Earth

7. Some mains cables only have two wires. Which wire is missing?
Earth
8. Which one of the 3 mains wires are circuit breakers and fuses always connected into?
Live
9. What happens to a fuse if the current exceeds the rating of the fuse?
It melts, thereby breaking the circuit
10. Which acts the fastest, a fuse or a circuit breaker?
circuit breaker
11. Which appliances are usually earthed?
• Those with metal cases
12. What is the purpose of the earth wire?
By providing a low-resistance path for the current to flow in the event of a fault, it enables the fuse to blow and break the circuit
13. What happens when an electrical charge flows through a resistor?
It gets hot
14. In a filament lamp, what is most of the electrical energy converted into?
Heat (wasted)
15. What is the unit of power?
Watt (W)
16. What is the unit of energy?
Joule (J)
17. What is the unit of electrical current?
Amperes (Amps) (A)
18. What is the unit of electrical charge?
Coulomb (C)
19. What is the relationship between energy (E), potential difference (V) , and charge (Q)
E = V x Q
20. Are electrons negatively or positively charged?
Negatively
21. What causes some insulating materials to become electrically charged when they are rubbed together?
Electrons are rubbed off one material and onto the other
22. What happens when two electrically charged objects (that have the same charge) are brought together?
They repel each other
23. Give an example of a type of material that electrical charges can move through easily
Metals
24. What is electric current?
A flow of electric charge
25. What is the unit of electrical current?
Ampere (Amp) (A)
26. How is the size of a current (I) calculated from the total charge (Q) and time (t)?
I = Q/t
27. What is the standard unit of electrical charge?
Coulomb (C)
28. What is potential difference another name for ?
Voltage
29. What component is this graph for?
Resistor
30. What is the unit of resistance?
Ohm
31. If a component has a larger resistance, will the current be larger or smaller?
Smaller
32. In a series circuit, what do you know about the current at different points?
It is always the same
33. In a series circuit how is the total resistance calculated?
By adding up the individual resistances
34. For components connected in parallel what do you know about the potential difference across each component?
They are all the same
35. What component is this graph for?
Filament bulb
36. Which component only allows current to flow one way?
Diode
37. What component is this graph for?
Diode
38. What happens to the resistance of an LDR as light intensity increases?
The resistance decreases
39. What happens to the resistance of a thermistor as temperature increases?
The resistance decreases
40. Which component emits light when a current flows through it in a forward direction?
Light Emitting Diode (LED)

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