# Physics revision P1.1 + P1.2 energy and efficiency

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• Created by: melisa
• Created on: 18-09-13 22:40
The useful energy transfer that happens in an electric lamp is:
The correct answer is electricity → light.
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'Wasted energy' becomes less useful because:
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Which equation can be used to calculate the efficiency of an energy transfer?
efficiency = useful energy out ÷ total energy in
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In a certain device, 25% of the energy is usefully transferred. The energy efficiency of this device is:
25%
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A coal-fired power station is 40% efficient. This means that:
40% of the chemical energy stored in coal is transferred to electrical energy.
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## Other cards in this set

### Card 2

#### Front

'Wasted energy' becomes less useful because:

### Card 3

#### Front

Which equation can be used to calculate the efficiency of an energy transfer?

### Card 4

#### Front

In a certain device, 25% of the energy is usefully transferred. The energy efficiency of this device is:

### Card 5

#### Front

A coal-fired power station is 40% efficient. This means that: