Efficiency & Energy ResourcesEdexcel GCSE Physics: Flashcards

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Give the equation for efficiency.

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Give the equation for efficiency.: Efficiency = useful energy transferred by the device divided by total energy supplied to the device.
Can any device be 100% efficient? Why/why not?: No — some energy is always dissipated, usually to the thermal store of the surroundings.
Name two ways efficiency can be increased.: Lubrication to reduce friction, and improved thermal insulation to reduce unwanted thermal energy transfer.
Name three non-renewable energy resources.: Fossil fuels (coal, oil, natural gas) and nuclear fuel.
Name five renewable energy resources.: Bio-fuel, wind, hydroelectricity, tides, the Sun (solar).
Define a non-renewable energy resource.: A resource being used up faster than it can be naturally replaced, so it will eventually run out.
Define a renewable energy resource.: A resource that is naturally replenished and will not run out.
Why are fossil fuels a concern despite being widely used?: Burning them produces carbon dioxide emissions linked to climate change, and they are finite.
What is a key advantage of nuclear power?: It provides a large, reliable electricity supply without direct carbon dioxide emissions.
What is a key disadvantage of nuclear power?: Concerns over radioactive waste disposal and safety.
What general trend has occurred in global energy resource use in recent decades?: Increasing use of renewable resources and a gradual move away from reliance on fossil fuels.
A device is supplied with 200 J and usefully transfers 50 J. What is its efficiency as a percentage?: 25% (50 divided by 200 = 0.25, times 100 = 25%).