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3 Conservation of energy

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Question 32
F

A filament lamp is supplied with 60 J of energy each second.

It transfers 6 J of energy each second usefully as light. The rest of the energy is transferred by heating to the thermal store of the surroundings.

a.

Calculate the efficiency of the filament lamp.

[2]
b.

An LED lamp also transfers 6 J of energy each second usefully as light.

The efficiency of the LED lamp is 0.75.

Calculate the total energy supplied to the LED lamp each second.

[3]
c.

Explain why the energy transferred by heating from the filament lamp is described as wasted.

[2]
Markscheme

3 Conservation of energy Questions

  1. GCSE
  2. /Physics
  3. /3 Conservation of energy

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