OCR GCSE Physics A key terms

The potential difference across a transformer coil connected to the input supply.

The straight line through the optical centre of a lens, perpendicular to the lens.

The point at which rays initially parallel to the principal axis converge, or appear to have diverged from, after passing through a lens.

For an object balanced against turning, the total clockwise moment about a pivot equals the total anticlockwise moment.

The characteristics used to describe or identify a material, such as its state, melting point, density and chemical behaviour.

A relationship in which quantities change by the same multiplicative factor.

A subatomic particle in the nucleus that has a positive charge.

The number of protons in a nucleus; it determines the element and its nuclear charge.

A forming star that is contracting under gravity but has not yet begun sustained hydrogen fusion in its core.

A longitudinal seismic wave in which particles vibrate parallel to the direction of travel; it can travel through solids and liquids.

The quantity of electric charge transferred past a point; its symbol is $Q$ and its unit is the coulomb (C).

The use of reflected electromagnetic waves to detect an object and determine information such as its position.

Energy carried away from a source as waves or particles; electromagnetic radiation includes gamma rays.

A state in which a body absorbs and emits radiation at equal rates, so radiation alone causes no temperature change.

The amount of radiation received during an exposure.

The unwanted presence of radioactive material on or inside an object or living thing.

The spontaneous emission of radiation from an unstable atomic nucleus.

A radioactive substance introduced into the body so that radiation detected outside it can reveal where the substance has travelled or collected.

Treatment that uses ionising radiation to damage or destroy unwanted tissue, such as a cancerous tumour.

An electromagnetic wave that can be produced by oscillating electric charges and can cause charges in a receiving aerial to oscillate.

The distance from the centre of an object to its edge.

Variation that makes repeated measurements differ unpredictably; its effect can be reduced by taking repeats and calculating a mean.

A region of a longitudinal wave where parts of the medium are further apart.

A comparison describing how much one quantity changes per unit of another quantity, such as metres travelled per second.

The amount of thermal energy transferred each second from a warmer object or place to a cooler one.

A comparison between quantities written in a stated order, such as remaining : original.

A straight line representing the direction in which light travels, with an arrowhead showing that direction.