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Energy resources and energy transfers

Energy resources and energy transfers

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Question 21

An offshore wind turbine generates electricity for the National Grid.

a.

The useful energy transfer in the wind turbine is:

  • A thermal energy to electrical energy
  • B kinetic energy to electrical energy
  • C gravitational potential energy to electrical energy
  • D chemical energy to electrical energy
[1]
b.

The generator in the wind turbine transfers 36 MJ36\text{ MJ}36 MJ of energy in 4 minutes4\text{ minutes}4 minutes. The generator current is 250 A250\text{ A}250 A.

Calculate the output voltage of the generator.

[4]
c.

The generator output voltage is then increased to 400 kV400\text{ kV}400 kV for transmission. Explain why electrical energy is transmitted using very high voltages.

[2]
d.

The generator provides a direct current (d.c.). This d.c. is changed to an alternating current (a.c.). The frequency of the alternating current is 50 Hz50\text{ Hz}50 Hz.

Explain the meaning of 50 Hz50\text{ Hz}50 Hz alternating current.

[2]
e.

Explain why the d.c. from the generator must be changed to a.c. before it is transmitted.

[2]
Markscheme

Energy resources and energy transfers Questions

  1. IGCSE
  2. /Physics
  3. /Energy resources and energy transfers

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