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

No mark for just 'wires'

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)