no device can be more than 100% efficient because you can get more energy from a machine than you put into it

• if friction between moving parts causes heating , lubricate the moving parts to reduce friction

• if the resistance of a wire causes the wire to get hot when a current passes through it , use wires with as little electrical resistance as possible

• if air resistance causes a force on a moving object that opposes and the energy is transferred to the surroundings, streamline the moving objects to reduce air resistance

• if sound is created by machinery , cut out noise by tightening loose parts etc

when you turn a handle you wind the clockwork spring in it and increase the epe of the spring when the spring unwinds energy from the epe store is transferred to kinetic energy and it turns a small electric generator in the radio

one disadvantage is that you have to wind up the spring every time the store of energy has been used

the energy supplied to a motor per second is the power supplied to it

the more powerful the motor is the faster it works and the faster the rate at which is transfers energy

POWER (W) = ENERGY TRANSFERRED TO APPLIANCE (J) / TIME TAKEN FOR ENERGY TO BE TRANSFERRED (s)

an appliances useful output power is the useful energy per second transferred by it

its total input power is the energy per second supplied to it

EFFICIENCY = (USEFUL POWER OUT / TOTAL POWER IN) X 100%

power wasted = total power in - useful power out