Physics key terms

Energy transferred because of a temperature difference or during a change of state, measured in joules.

A state in which there is no net energy transfer between a body and its surroundings because they are at the same temperature.

The increase in volume of stellar material when heating makes its particles move faster and spread further apart.

An image made by detecting infrared radiation emitted by objects, allowing differences in temperature to be shown.

A delay between energy being supplied to an object and the resulting temperature rise being fully detected.

A material or structure used to reduce the rate of energy transfer by heating.

A material that reduces the rate at which thermal energy is transferred.

Electromagnetic waves emitted by a body because of its temperature.

The energy store associated with the movement and arrangement of particles in an object.

A resistor whose resistance decreases as its temperature increases.

An image made using infrared radiation that shows differences in the surface temperatures of objects.

The distance a vehicle travels during the driver's reaction time, before the brakes are applied.

The time a driver takes to recognise a hazard, react and apply the brakes.

A simplified model in which all refraction is represented as occurring at one line through the lens.

A pair of equal-sized forces in opposite directions that two interacting objects exert on each other. The forces act on different objects.

The duration of an energy transfer or of work being done, measured in seconds (s) in the power equations.

The difference between the times at which the same signal reaches two detectors.

The duration between two events, measured in seconds (s).

The duration over which an energy transfer takes place; in the power equation it is measured in seconds (s).

Harm to cells which can impair or destroy them and, if sufficiently widespread, damage tissue.

Fine powder used to form the printed image in a photocopier or laser printer.

The complete length of the route travelled, irrespective of direction.

All the energy supplied to a device or process.

All the energy transferred into a device.

The amount of energy used by a population over a stated period, often one year.

All the energy supplied to a device or system.

The complete reflection of light at a boundary when it travels towards a lower-refractive-index material at an angle of incidence greater than the critical angle.