A chemical cell that is used once and discarded when its reactants are used up, such as an alkaline cell.
62 of the Physics glossary’s terms, each with the part of the syllabus where you first meet it.
A longitudinal seismic wave; it travels faster than S waves and through solids and liquids.
A graph of pressure against volume on which each point is a state of a gas and each line a change of state.
Components connected across the same two points, so that they share the same pd and the branch currents add to the total.
The original nucleus that undergoes radioactive decay.
The distance at which 1 AU subtends an angle of one arc-second; .
The SI unit of pressure: .
The difference between the distances travelled by two waves from their sources to a given point.
How far a radiation travels into matter before it is absorbed, measured by the thickness of material needed to absorb it.
The difference between an experimental and an accepted value as a percentage of the accepted value; it measures accuracy.
The fractional uncertainty expressed as a percentage, .
A collision in which the bodies stick together and move off with a common velocity; the loss of kinetic energy is the largest that momentum conservation allows.
The point of an orbit around the Sun that is closest to the Sun, where the orbiting body moves fastest.
The time for one complete cycle of a repeating motion, such as one revolution in circular motion, in seconds.
The constant that sets the strength of the magnetic field produced by a current in a vacuum.
A property of a medium that determines the electric force between charges in it; the larger the permittivity, the weaker the force.
The constant
The stage an oscillation has reached in its cycle, expressed as an angle in radians, .
The angle , in radians, that fixes the position of a simple harmonic oscillator in its cycle at .
A change between solid, liquid and gas, which happens at constant temperature while energy changes the intermolecular potential energy of the particles.
The difference in phase between two oscillations or two points on a wave of the same frequency, in radians: .
An evacuated tube containing a photosensitive cathode and an anode, used to measure the current and energy of photoelectrons.
The electric current carried by photoelectrons that travel from the cathode to the anode of a photocell.
The emission of electrons from a metal surface when electromagnetic radiation above a threshold frequency falls on it.
An electron released from a surface by the photoelectric effect.
A discrete packet (quantum) of electromagnetic radiation, with energy and momentum ; it travels at in a vacuum and has no rest mass.
The number of photons arriving per second; at a fixed frequency it is proportional to the intensity of the beam.
A quick trial of a method before the main data collection, used to check that it works, to find a suitable range and to estimate the scatter in the results.
How high or low a sound is heard to be; a higher frequency is heard as a higher pitch.
Presenting another person's words, ideas or work as one's own without clear acknowledgement, deliberately or by accident.
The constant that links the energy of a photon to its frequency () and the momentum of any particle to its wavelength (
A glowing shell of gas thrown off by a low-mass star at the end of its red-giant stage, leaving a white dwarf at its centre.
A gas so hot that its atoms are fully or largely ionised, made of free nuclei (or ions) and free electrons.
Thomson's model of the atom (1904): a sphere of evenly spread positive charge with electrons embedded in it. Alpha-particle scattering showed it to be wrong.
A charge whose size is negligible compared with the distances involved, so that it can be treated as concentrated at a single point.
A body whose size is negligible, so that all its mass can be treated as being at one point.
Where a body is relative to a chosen origin, given as a distance with a direction (or sign).
A process in which a change causes effects that increase the original change, such as warming that reduces albedo and so causes more warming.
The antiparticle of the electron, with the same mass and a charge of ; emitted in β⁺ decay.
(1) The laws of physics are the same in all inertial reference frames; (2) the speed of light in a vacuum is the same for all inertial observers.
The work done per unit charge in moving a positive charge between two points, ; measured in volts, where .
Two or more resistors in series across a supply, sharing its pd in the ratio of their resistances; the output is the pd across one of them.
The rate of change of potential with distance, ; the field strength is minus the potential gradient.
A resistor with a sliding contact; with a supply across its whole length it acts as a potential divider giving any output pd from zero to the supply pd.
The rate of doing work or of transferring energy: , and for a force moving at velocity . Measured in watts.
How closely repeated measurements of the same quantity agree with one another; it is limited by random errors.
The force acting perpendicular to a surface per unit area of the surface, ; measured in pascals (Pa).
For a fixed mass of gas at constant volume, pressure is proportional to absolute temperature: = constant.
The commonest type of power reactor, in which water under high pressure acts as both moderator and coolant and transfers energy to a separate steam loop.
A chemical cell that is used once and discarded when its reactants are used up, such as an alkaline cell.
Data collected or generated by the investigator, by measurement or from a simulation they run.
The positive whole number that labels an energy level; in the Bohr model the hydrogen energy is eV.
Energy cannot be created or destroyed, only transferred from one form or body to another, so the total energy of an isolated system is constant.
For a body in rotational equilibrium, the sum of the clockwise torques about any axis equals the sum of the anticlockwise torques about that axis.
When two or more waves meet at a point, the resultant displacement is the vector sum of the displacements that each wave would produce on its own.
Values calculated from raw data, such as means, derived quantities and their uncertainties.
A body that has been launched and then moves under gravity (and, in real cases, fluid resistance) with no other force acting.
The length of an object measured in the inertial frame in which it is at rest; the longest length any observer measures for it.
The time interval between two events measured in the inertial frame in which they happen at the same place; the shortest time any observer measures between them.
The number of protons in a nucleus; it identifies the element.
The sequence of fusion reactions by which the Sun converts hydrogen into helium-4, releasing 26.7 MeV per helium nucleus.
A collapsing, heating ball of gas that has not yet started hydrogen fusion in its core.
A single short disturbance that travels through a medium, as opposed to a continuous wave.