P3 Electricity
Fact Sheet
Motors and the motor effect
1. What is current? [1]
The flow of charge in a circuit
2. What is around a current carrying wire? [1]
A magnetic field
3. What charged particles flow in a circuit? [1]
Electrons
4. The coil in a motor does not experience a
force if it is [1]
parallel to the magnetic field.
Creating an electric current or potential
5. What does induction mean? [1]
difference in a conductor when it is
exposed to a magnetic field.
Coil of wire
6. What are the parts of a motor? [2]
Inside 2 magnets (a magnetic field)
When a current-carrying wire in the
7. What is the Motor effect? [1]
presence of a magnetic field experiences
a force, making it move
 Increase the size of the current
8. How can you increase the speed of a motor?
 Increase the strength of the
[2]
magnet
 Change the direction of the
9. How can you change the direction of a
current
motor? [2]
 Change the direction of the
magnetic field
10. What rule that shows the direction of
Fleming’s Left hand rule
values in the motor effect? [1]
11. What do the fingers stand for in Flemings’
left hand rule? [3]
12. What is an electromagnet? [1]
13. Give two uses of an electromagnet [2]
 First finger = magnetic Field
 seCond finger = Current
 thuMb = Motion
A coil of wire wrapped around an iron
core which both become magnetised
when a current is flowing
 Door bell
 RCCB
Transformers
14. What does d.c. stand for? [1]
Direct current
15.
Alternating current
What does a.c. stand for? [1]
16. What are transformers made of? [2]
17. What does a step up transformer do? [1]
Iron core
Primary coil and secondary coil made of
insulated copper wire
A transformer that increases the
voltage, which in turn decreases the
current.
18. This is the name given to the “input” coil
on a transformer. [1]
Primary Coil
19. This is the name given to the “output” coil
on a transformer. [1]
Secondary coil
20. What is the core of a transformer or
electromagnet made from? [1]
Iron
21. Does a transformer use a.c. or d.c.
current?
a.c.
22. What is the equation relating voltage and
number of turns for a transformer? [1]
23. What type of current must flow through
the primary coil of a transformer? [1]
Vp / Vs = np / ns
Alternating current
 In the National Grid
24. Where do we use transformers? [2]
 As chargers for mobile phones
and computers
 They are small and portable
25. Why are switch mode transformers better
 They are lighter
than regular transformers? [3]
 They use very little power when
no load is connected
It is a much smaller transformer with a
26. What is special about a switch mode
high frequency that quickly turns on and
transformer? [1]
off to change the voltage
27. Where do you often find switch mode
In plugs – such as mobile phone
transformers? [1]
chargers
Skills - Calculations
28. If a transformer with 100 turns on the
primary coil with a primary voltage of 20V
and the secondary voltage is 40 V, what is
the number of turns on the secondary
coil?[1]
29. If a transformer with 20 turns on the
primary coil with a primary voltage of 100V
and the secondary voltage is 40 V, what is
the number of turns on the secondary
coil?[1]
30. If a transformer with 10 turns on the
primary coil with a primary voltage of 200V
and the secondary voltage is 400 V, what is
the number of turns on the secondary
coil?[1]
31. If a transformer with 100 turns on the
primary coil with a primary voltage of 20V
and the number of turns on the secondary
coil is 50, what is the secondary voltage? [1]
32. If a transformer with 40 turns on the
primary coil with a primary voltage of 2V
and the number of turns on the secondary
coil is 200, what is the secondary
voltage?[1]
33. If a transformer with a primary voltage of
20V and the number of turns on the
secondary coil is 50, with a secondary
voltage of 10V what is the primary number
of turns? [1]
34. If a transformer with a primary voltage of
10V and the number of turns on the
secondary coil is 5, with a secondary
voltage of 2V what is the primary number
of turns? [1]
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