Physics

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Forms of energy

Kinetic

Chemical

Heat/thermal

Elastic potential energy

nucleur

elctrical

magnetism

gravitational potiential energy

light

sound

Law of conservation of energy

Energy can be found in various different forms. Energy cannot be created or destroyed (it can only be transferred from place to place or transformed from one to another.

The eficency of a device is a measure of how much of the energy we put into it is transformed 'usefully'.

efficency = Usefeul energy out

Total energy in

Power is a measure of the energy transferred/transformed by a device per second.

Power= energy transferred power = watt (w)

time taken

Electrical energy is used for so many things because:

it is easy to transfer from place to place

it can be easily controlled

it can be easily transformed into lots of other forms of energy

Energy companies measure electrical energy in kilowatt hours (kWh).

Energy used = Power x Time used

(kwh) (kW) (hrs)

Cost = N.o. of kWh used x cost per kWh

(p) (p)

1kWh costs 8p

Workdone = force x distance moved in direction of force

(J) (N) (m)

Gravitational potiential energy = mass x gravitational field strength x change in height

Ep = m x 10 x ^h

The efficency of human muscle is approximately 20%. This means that your muscles use 5 times as much energy as the transfer usefully.

Kinetic energy = 0.5 x mass x (speed)2

Hookes law

The extension of a spring is directly proportional to te force applied provided its limit of proportionality is not exceeded.

The spring constant ,k, is a measure of how hard it is to strech a spring. The bigger the spring constant, the stiffer the spring.

Elastic potential energy = 0.5 x spring constant x (estension)2

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Energy Resources

A renewable energy resource is one which will not run out.

A non-renewable energy resource will run out.

In fossil fuels power station fuel is burned to produce electricity. This is used to heat water in a boiler to turn it into steam.

The steam is used to turn a turbine which then turns a generator. This transformskinetic energy into electrical energy.

Non-renewable energy