Physics - P1.2 - Using Energy - Revision Cards in GCSE Physics

P1.2.1 - Forms of Energy

Types of energy - light, sound, kinetic, nuclear, electrical, gravitational potential, elastic potential, chemical - last three = forms of stored energy
Energy can be transferred from one form to another
Any object above the ground has gravitational potential energy
Falling object transfers gravitational potential energy -> kinetic energy

1 of 4

Not possible to create or destroy - possible to transfer it from one form or place to another
Conservation of energy - total amount of energy is always the same, applies to all energy transfers
Falling object - gravitational potential energy -> kinetic energy
Stretching an elastic band - chemical energy -> elastic potential energy
Solar cell - light energy -> electrical energy
Swinging pendulum - gravitational potential energy -> kinetic energy and back as it swings

2 of 4

Machine - something that transfers energy from one form or place to another
Energy we get out of a machine consists of: useful energy - transferred to place and form wanted, wasted energy - not usefully transferred
Useful and wasted energy eventually transferred to surroundings and make them warm up
Energy spreads out - becomes more difficult to use for further transfers
Energy often wasted because of friction between moving parts of machine - warms machine and surroundings
Friction may be useful - brakes of bike or car
Some kinetic energy of vehicle transferred to energy heating brakes

3 of 4

Joules (J) - unit for all forms of energy
Input energy - energy supplied to machine
Input energy = useful energy transferred + energy wasted
Less wasted energy = more efficient
Efficiency = useful energy transferred by appliance
total energy supplied to appliance X 100
Left as a fraction or multiplied by 100 to give %
No appliance = 100% efficient - except electrical heater - usefully transfers all electrical energy supplied to heating surroundings
Energy transferred through appliance represented with sankey diagram

4 of 4