OCR GCSE Physics A key terms

The internationally standardised system of measurement, including the metre, kilogram and second.

A pair of separate contacts that maintains the connections between the ends of a rotating coil and the external circuit.

The iron placed inside an electromagnet that becomes magnetised while current flows and readily loses its magnetism when the current is switched off.

The Sun and the objects held in orbit around it by gravity, including planets and smaller bodies.

A long coil containing many turns of insulated wire, which produces a magnetic field when a current flows through it.

A method of detecting underwater objects or measuring water depth using sound waves and their echoes.

A wave produced by vibrations that travel through a medium as alternating regions of higher and lower pressure.

An object or process that emits electromagnetic waves, supplying the energy carried by them.

A brief discharge in which electric charge passes through air between objects.

The energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, without changing its state.

The energy required to change the state of 1 kg of a substance without changing its temperature.

The specific latent heat for a change between the solid and liquid states.

The specific latent heat for a change between the liquid and gas states.

Orderly reflection from a smooth surface, in which parallel incoming rays remain parallel after reflection.

The distance travelled per unit time, measured in metres per second (m/s).

The speed at which all electromagnetic waves travel through a vacuum, approximately $3.00 \times 10^8\ \text{m/s}$.

A two-part rotating contact that swaps a coil’s connections to an external circuit every half-turn.

A measure of a spring’s stiffness, found by dividing force by extension in the straight-line region of a force–extension graph; its unit is N/m.

A circular path around another body in which the orbiting object stays at a constant distance from its centre.

A way of writing a number as a value between 1 and 10 multiplied by a power of ten.

A wave pattern produced by overlapping waves travelling in opposite directions, with fixed nodes and antinodes.

An imbalance of electric charge that remains on an object rather than flowing away.

The build-up of electric charge on an object, rather than a continuous flow of charge through a circuit.

A transformer that produces a lower output potential difference than its input potential difference.

A transformer that produces a higher output potential difference than its input potential difference.

The elimination of all viable microorganisms from an object, substance or surface.

A measure of how strongly a spring or system resists extension: a stiffer system extends less under the same force.