57 of the Physics glossary’s terms, each with the part of the syllabus where you first meet it.
A reversible cycle of two isothermal and two adiabatic changes; the most efficient possible cycle between two reservoir temperatures.
The maximum efficiency of a heat engine between reservoirs at and : , with temperatures in kelvin.
The bright region at the centre of a single-slit diffraction pattern, twice as wide as each side maximum and much brighter.
The point at which the whole mass of a body can be treated as concentrated; the weight of a body acts through it.
The acceleration of a body moving in a circle, directed towards the centre: .
The resultant force on a body moving in a circle, directed towards the centre and perpendicular to the velocity: . It is provided by real forces such as tension, friction or gravity.
A sequence of fissions in which neutrons released by one fission cause further fissions; it is self-sustaining when, on average, one neutron from each fission causes another.
The largest mass, about 1.4 solar masses, that a white dwarf can have while being supported by electron pressure.
A charged particle that is free to move through a material and so carry a current, such as a free electron in a metal or an ion in an electrolyte.
The charge of a particle divided by its mass, , in ; it sets the radius and period of the particle’s path in a magnetic field.
Charging a conductor by touching it with a charged object, so that some of the charge spreads on to it; the conductor gains charge of the same sign.
Charging two different materials by rubbing them together, which transfers electrons from one to the other and leaves them with equal and opposite charges.
For a fixed mass of gas at constant pressure, volume is proportional to absolute temperature: = constant.
A source of emf that converts chemical energy into electrical energy through reactions at its two electrodes.
A drawing of how components are connected, using standard symbols and straight wires, without showing the physical layout.
The form of the second law stating that thermal energy cannot spontaneously transfer from a colder region to a hotter one.
A pipe closed at one end and open at the other; the closed end is a displacement node, the first harmonic has and only odd harmonics are present.
A system that can exchange energy with its surroundings but not matter, such as a gas sealed in a cylinder with a movable piston.
The ratio of the friction force to the normal force for two surfaces: for the maximum static friction, while sliding. It has no unit.
Describes waves or sources with the same frequency and a constant phase difference.
The instruction word that starts a question part (state, calculate, explain, discuss …) and defines the kind and depth of answer expected.
One of two perpendicular vectors that together add up to a given vector; a vector at angle to the horizontal has components and .
A region of a longitudinal wave where the particles of the medium are closer together than normal, so the pressure is higher.
The scattering of an X-ray or gamma-ray photon by a free or loosely bound electron, in which the photon loses energy, so its wavelength increases, and the electron recoils.
The increase in wavelength of a Compton-scattered photon:
The constant , equal to the Compton shift for a photon scattered through 90° by an electron.
The change from gas to liquid, during which energy equal to the latent heat of vaporization is released.
The transfer of thermal energy through a material, without bulk movement of the material, by collisions between particles and, in metals, by free electrons.
A material with a large number of mobile charge carriers, so that it carries a large current for a small pd.
The total angular momentum of a system about an axis stays constant if no resultant external torque acts on it about that axis.
The principle that the total electric charge of an isolated system stays constant: charge can be transferred but never created or destroyed.
The total momentum of a system stays constant provided no resultant external force acts on it.
A force, such as gravity or an elastic force, whose work on a body moving between two points depends only on those points and not on the path taken.
Superposition of waves that meet in phase, giving a resultant amplitude larger than either wave's; for in-phase sources it occurs where the path difference is .
A force that acts only while two bodies touch, such as the normal force, friction, tension, an elastic force, fluid resistance or buoyancy.
A spectrum containing all wavelengths over a wide range with no gaps, emitted by a hot, dense object such as a lamp filament or a star's interior.
A rod of a strongly neutron-absorbing material, such as boron or cadmium, moved into or out of a reactor core to control the rate of fission.
A variable that could affect the dependent variable and is therefore kept constant (or monitored) so that only the independent variable changes.
The transfer of thermal energy by the bulk movement of a fluid, driven by differences in density between warmer and cooler parts of the fluid.
A continuous circulation of fluid in which warmer, less dense fluid rises and cooler, denser fluid sinks, carrying energy round the loop.
The direction of current used in circuit diagrams: the direction positive charge would flow, from the positive terminal of a source round the circuit to the negative terminal. Electrons in a metal move the opposite way.
A fluid pumped through a reactor core to carry away the energy released by fission.
The SI unit of charge: the charge that passes a point when a current of 1 A flows for 1 s.
The electrostatic repulsion that two positively charged nuclei must overcome to get close enough for the strong nuclear force to bind them.
The constant in Coulomb's law,
The electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation: .
The number of decays registered by a detector per unit time; proportional to the activity for a fixed arrangement, but smaller than it.
Two equal and opposite parallel forces whose lines of action are separated; it produces a torque about any axis but no resultant force.
A point of maximum positive displacement on a transverse wave.
The angle of incidence, in the medium where a wave is slower, for which the angle of refraction is 90°. For light, .
The amount of damping at which a displaced system returns to equilibrium in the shortest time without oscillating.
The smallest mass of fissile material, in a given shape and arrangement, in which a chain reaction is self-sustaining.
Uniform electric and magnetic fields at right angles to each other, arranged so that their forces on a moving charge act in opposite directions.
A part of a vehicle designed to fold up in a controlled way in a collision, lengthening the stopping time and so reducing the average force on the occupants.
A pivoted frame that measures a magnetic flux density by balancing the magnetic force on a current-carrying wire against the weight of a known mass.
One complete oscillation, ending when the body is next at the same position moving in the same direction.
A series of changes that returns a gas to its starting state, so and the net work equals the area enclosed on a P–V diagram.