GCSE Questions: Energy Sources
Q24. The diagram shows part of the National Grid linking a power station to consumers.
(a) Name the parts of Figure 2 labelled A and B.
A = transmission/power lines/cables 
B is the step-down transformer
[2 marks]
(b) Electricity is transmitted through A at a very high potential difference.
Which of the following is the advantage of transmitting electricity at a very high potential difference?
(Tick one box)
| A high potential difference is safer for consumers. |
|
| Less thermal energy is transferred to the surroundings. |
|
| Power transmission is faster. |
|
[1 mark]
(c) The power station generates electricity at a potential difference of 25 kV.
The energy transferred by the power station in one second is 500 MJ.
Calculate the charge flow from the power station in one second.
P = E/t
P = IV
Charge flow in coulombs/second is current in amps.
500 x 106= I x 25 x 103
I = 500/25 x 103
I = 20 x 103 A
Therefore the charge movement in one second = 20 kC
[4 marks]
(Total 7 marks)
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