Conservation of Energy and Efficiency

Science

Energy can be created, but not destroyed.

Energy can be created, destroyed and transferred.

Energy cannot be created or destroyed, only transferred.

when energy is transferred to many different stores

when energy is transferred to stores that are not useful

when energy is transferred to useful stores

by heating to the kinetic energy store of the surroundings

by heating to the thermal store of the surroundings

electrically to the kinetic energy store of the surroundings

mechanically to the thermal store of the surroundings

efficiency = energy input ÷ useful energy output

efficiency = total energy output ÷ energy input

efficiency = useful energy output ÷ energy input

efficiency = useful energy output ÷ not useful energy output

to show the direction of energy transfers

to show the time taken for energy to transfer

Energy can be transferred from one store to another.

Which of these statements about energy is true?

Chemical energy is given out to the surroundings.

Gravitational potential energy is given out to the surroundings.

Nuclear energy is given out to the surroundings.

Thermal energy is given out to the surroundings.

A light bulb has energy transferred to it electrically. How is energy wasted by a light bulb?

A washing machine transfers energy to its thermal and kinetic stores to wash clothes. How is energy wasted by a washing machine?

Match the energy store to a real life example.

a microwave oven using microwaves to heat food

Match the energy transfer to a real life example.