Physics key terms

The direction in which positive charge is treated as flowing, from the positive terminal of a supply to its negative terminal.

A lens that brings rays travelling parallel to its principal axis together at a principal focus.

A numerical relationship used to change a measurement from one unit to another without changing the quantity represented.

A lens that brings rays travelling parallel to its principal axis together.

A fluid that carries thermal energy away from the reactor core.

A graph showing how an object's temperature changes with time as it cools.

Earth's central region, associated with the source of its magnetic field.

A relationship in which two measured variables tend to change together.

Faint microwave radiation detected from all directions in space, understood as radiation left over from the hot early Universe.

Faint microwave radiation arriving from all directions in space, left over from the hot early Universe.

Microwave radiation detected from all directions in space, originating in the hot early universe.

High-energy radiation arriving from space, including fast-moving particles from the Sun and beyond.

High-energy radiation arriving at Earth from space.

The unit of electrical charge. One coulomb passes a point when a current of one ampere flows for one second.

The number of detections recorded by a radiation detector during a measured interval.

The number of events recorded by a detector each second.

The angle of incidence in the higher-refractive-index material for which the angle of refraction is 90°.

A part of a car designed to deform in a collision, increasing the time taken for the car to stop.

Parts at the front and back of a car designed to crumple in a collision. They increase the time taken for the car to stop, which reduces the rate of change of momentum and so the force on the people inside.

The formation of an ordered solid crystal structure from a liquid or solution.

The rate of flow of electric charge, measured in amperes (A).

A coil of conducting wire through which an electric current can flow.

A wire or other electrical conductor through which electric charge is flowing.

A graph showing how the current through a component changes as the potential difference across it changes.

A graph showing how the current through a circuit element varies with the potential difference across it.

One complete repetition of an alternating pattern, returning to the same value and direction of change.

The name given to an unknown cause proposed to explain why the expansion of the universe is accelerating.