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Energy resources and energy transfers

Energy resources and energy transfers

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Question 11

A tidal turbine generates electricity for the National Grid.

a.

The useful energy transfer in the tidal turbine is:

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

The generator in the tidal turbine transfers 54 MJ54\text{ MJ}54 MJ of energy in 2 minutes2\text{ minutes}2 minutes. The generator current is 300 A.

Calculate the output voltage of the generator.

[4]
c.

The generator output voltage is then increased to 275 kV275\text{ kV}275 kV for transmission. Explain why electrical energy is transmitted using very high voltages.

[3]
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 60 Hz.

Explain the meaning of 60 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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