Physics key terms

The material through which a wave travels, such as water or air.

The change from a solid to a liquid.

The curved surface of a liquid in a narrow container; for water, the scale is read at the bottom of the curve.

The SI unit of speed, meaning the number of metres travelled each second.

The SI unit of speed, meaning the number of metres travelled in one second.

An instrument used to measure very small lengths, such as the thickness or diameter of an object, to high precision.

A device that converts variations in sound pressure into a corresponding electrical signal.

Electromagnetic radiation between radio waves and infrared in the spectrum, used for communication and for heating food.

The three small bones in the middle ear—the malleus, incus and stapes—which transmit vibrations from the eardrum towards the inner ear.

Action taken to reduce the likelihood or severity of an unwanted effect.

A simplified representation used to describe, explain or predict how something behaves.

A material in a nuclear reactor that slows down neutrons so that they are more likely to cause further fission.

A particle made from two or more atoms chemically bonded together.

The turning effect of a force about a pivot, measured in newton-metres (Nm).

The turning effect of a force about a pivot, measured in newton-metres (Nm).

The product of an object's mass and velocity, measured in kilograms metres per second (kg m/s). It has a direction because velocity has a direction.

A change in momentum caused when a particle rebounds from a container wall.

A natural satellite that orbits a planet.

The force produced when a current-carrying conductor is placed in a magnetic field.

A device in which a current-carrying coil moves in a permanent magnet’s field and drives a cone or diaphragm to produce sound.

A microphone in which sound makes a coil move relative to a magnetic field, inducing an electrical signal.

A unit larger than the unprefixed unit, formed using a multiplier greater than one, such as a kilometre.

A change in the genetic material of a cell.

The transfer of an electrical effect between separate circuits when a changing current in one circuit produces a changing magnetic field that induces a potential difference in the other.

Meeting or acting at an angle of 90°.

One billionth of a metre, written as $10^{-9}$ m.

A network of cables and transformers that transfers electrical power from power stations to consumers.