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Closed system
A system in which there is no net change to the total energy
Law of conservation of energy
Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed
Useful energy transfer
When energy is transferred by a device to energy stores we want
Wasted energy transfer
When energy is transferred by a device to energy stores we don't want
Dissipate
When energy spreads out and is transferred to energy stores into less useful forms
Dissipated energy
Energy which is wasted and is usually transferred to the surroundings, causing them to heat up
Lubricate
When a substance is used to reduce wasted energy transfers by reducing the friction between moving parts
Insulate
When a substance is used to reduce wasted energy transfers by reducing the amount of heat that is transferred to the surroundings
Thermal conductor
A material that allows charge or heat to pass through it easily
Thermal insulator
A material that does not allow charge or heat to pass through it easily
Thermal conductivity
The rate of energy transfer by conduction through a material
Conduction
When heat is transferred through a material due to vibrating particles colliding and transferring energy from one particle to another
Convection
When heat is transferred through a moving liquid or gas due to differences in densities
Radiation
When heat is transferred from a hot object due to the object emitting infrared (heat) radiation
