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Physics ­ Core Revision notes
Heat transfer
Atmosphere protection

Radio waves, microwaves, infra-red radiation and visible light are part of the
electromagnetic spectrum. Electromagnetic waves are electric and magnetic waves that
travel through space.
The sun emits radiation in all parts of the electromagnetic spectrum and we are protected by…

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When a metal rod is heated at one end, the free electrons at the hot end gain kinetic
energy and move faster.
o These electrons diffuse and collide with other free electrons and ions in the cooler
part of the metal
o As a result they transfer the kinetic energy…

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o
Elastic (or strain) energy
Energy stored in springy objects when we stretch or squash them
o Electrical energy
Energy transferred by an electric current
o Thermal (heat) energy
Energy due to temperature. This is partly because of the random kinetic
energy of the particles of the object.
When energy…

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Worked example

An electric motor is used to raise an object. The object gains 60J of gravitational potential energy
when the motor is supplied 200J of electrical energy. Calculate the efficiency of the motor.

Solution:

Total energy supplied to the device = 200J

Useful energy transferred to the device =…

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Using electrical energy

Energy transferred (kilowatt-hours, kWh) = power of device (kilowatts, kW) * time in use
(hours)
One kilowatt-hour is the amount of electrical energy supplied to a 1 kilowatt device in one
hour. So 1 kilowatt-hour = 1000 joules/second x 60 x 60s = 3,600,000J
The electricity meter…

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Generating electricity
Fuel for electricity

In a coal or oiled fired power station the burning fuel heats water in the boiler to produce
steam. The steam drives a turbine that turns an electricity generator
In a gas-fired power station, we burn natural gas directly in a gas turbine engine. This…

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A wave generator uses the waves to make a floating section move up and down. This motion
drives a turbine which turns a generator. A cable between the generator and the shore
delivers electricity to the grid system.
Wave generators need to withstand storms and they don't produce a constant…

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Energy and the environment

Fossil fuel problems
o When coal, oil or gas a burnt the chemical reactions make `greenhouse gases' such
as carbon dioxide. These gases cause global warming.
o Burning fossil fuels can produce sulphur dioxide. This gas causes acid rain in the
atmosphere. We can remove the…

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Electromagnetic waves are electric and magnetic disturbances that transfer energy from one
place to another
Wavelength
o Electromagnetic waves do not transfer matter. The energy that they transfer
depends on the wavelength of the waves. This is why waves of different wavelengths
have different effects.
o The wavelength is the…

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o To kill cancer cells a narrow bean of gamma radiation is directed at the tumour. The
beam is aimed at it from different directions in order to kill the tumour but not the
surrounding tissue. Uses cobalt-60 which is stored in a thick lead container. When
not in use,…

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