# Physics 1 A

p1a physics, GCSE revision

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Physics 1a ­ Energy and energy resources
Heat Transfer
Thermal radiation is the transfer of heat by infrared waves, which are part of the
electromagnetic spectrum.
All bodies emit and absorb thermal radiation.
The hotter a body is the more energy it radiates. Heat radiation passes through a vacuum,
this is how we get our heat from the sun.
The transfer of heat radiation does not involve particles.
Dark, matt surfaces are good absorbers and good emitters of radiation. Light, shiny
surfaces are poor absorbers and poor emitters of radiation.
However they are also good emitters, and they will lose heat quicker than a shiny white
surface.
Conduction
Conduction is the transfer of heat through
a substance, usually a solid, gases and
liquids are poor conductors of heat.
When one end of a metal is heated, then
those end particles gain kinetic energy
and they vibrate each other and gain
more energy.
Metals also have delocalised (free)
electrons, which vibrate throughout the
metal and pass on their energy.
Poor conductors are called insulators.
Good insulators have pockets of air to
trap heat in, for example air pockets in
fibreglass.
Convection
Convection occurs in fluids, that is liquids and gases.
When a fluid is heated it expands and becomes less dense, due to this lower density, it
rises and it is replaced by cooler fluid. This process repeats and you get what are called
convection currents.
Heat Transfer by design
Heat transfer by conduction can be reduced by using insulators
Heat transfer by convection can be reduced by preventing convection currents from forming,
for example trapping air in pockets.
Heat transfer by radiation can be reduced by using light shiny surfaces.
The converse can be applied to maximise heat loss to keep things cool.
Using Energy
Forms of energy
Chemical energy is energy stored in fuel (including food). This energy is released when
chemical reactions take place.
Kinetic energy is the energy of a moving object.
Gravitational potential energy is the energy of an object due to its position.
Elastic (or strain) energy is the energy stored in a springy object when we stretch or
squish it.
Electrical energy is energy transferred by an electric current.

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Thermal (heat) energy of an object is energy due to its temperature. This is partly because
of the random kinetic energy of the particles of the object.
Conservation of energy
Scientists have done lots of tests to find out if the total energy after change is the same as
the energy before the change. All the tests so far show it is the same.
This important result is known as Conservation of energy. It tells us that energy cannot

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Electrical energy is energy transfer due to an electric current
Uses of electrical devices include heating, lighting, making objects move and creating
sound and visual images.
Electrical power
The more powerful a device, the faster the rate at which it transforms energy.
We measure power of a device in watts (W) or kilowatts (kW).
1 kilowatt (kW = 1000 watts (W)
For any device,
Its input power if the energy per second supplied to it.…read more

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Water is turned into steam in the boilers
2. The steam drives the turbines
3. The turbines spin the generators, which produce the electricity
4. The electricity goes to the transformers to produce the correct voltage
Generating Electricity
Fuel for electricity
In a coal or oilfired power station, the burning fuels heats water in a boiler to produce
steam. The steam drives a turbine that turns an electricity generator
In a Gasfired power station, natural gas (fossil fuel) is burned in a gas turbine.…read more

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A solar heating panel heats water that flow through it.…read more