Physics (school) glossary
64 key terms from Physics (school), A to Z. Each is explained in one plain sentence and links to its free lesson.
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A
- AccelerationMotion and measurement
- How quickly velocity changes.
- Alpha, beta and gammaAtoms and radioactivity
- Alpha is a helium nucleus (2 protons, 2 neutrons), stopped by paper.
- Amplitude, wavelength and frequencyWaves, sound and light
- Amplitude is the wave's maximum displacement from rest.
- Atomic number and mass numberAtoms and radioactivity
- Atomic number is the number of protons.
C
- Changes of stateParticles and heat
- Melting, freezing, boiling, condensing and subliming change the state without changing the substance.
- Circuit symbols and componentsElectric circuits
- Standard symbols draw circuits.
- ConductionParticles and heat
- Heat passing through a solid as vibrating particles bump into their neighbours.
- Conservation of energyEnergy, work and power
- Energy is never made or destroyed.
- ConvectionParticles and heat
- Heat carried by moving liquid or gas.
D
- DensityParticles and heat
- How much mass is packed into each unit of volume.
- Distance-time graphMotion and measurement
- A graph with time along the bottom and distance up the side.
E
- Earth wireMains electricity and magnetism
- A safety wire that connects a metal case to the ground.
- EfficiencyEnergy, work and power
- The fraction of input energy that becomes useful output.
- Electric currentElectric circuits
- The flow of charge round a circuit, measured in amperes (A).
- Electrical powerElectric circuits
- The rate at which energy is transferred by a circuit.
- ElectromagnetMains electricity and magnetism
- A coil of wire with a current flowing makes a magnetic field like a bar magnet.
- Electromagnetic inductionMains electricity and magnetism
- A voltage is induced in a wire when it moves through a magnetic field, or when the field around it changes.
- Electromagnetic spectrumWaves, sound and light
- A family of transverse waves that all travel at the speed of light in a vacuum (300,000,000 m/s).
- Energy resourcesEnergy, work and power
- Renewable resources (wind, solar, hydroelectric, tidal, biomass) will not run out.
- Energy stores and transfersEnergy, work and power
- Energy cannot be seen, but it sits in stores (kinetic, gravitational, thermal, chemical, elastic) and moves between them.
- Equations of uniform accelerationMotion and measurement
- For steady acceleration: v squared = u squared + 2as, where u is start velocity, v is end velocity, a is acceleration and s is distance.
F
- ForceForces and Newton's laws
- A push or a pull, measured in newtons (N).
- Friction and dragForces and Newton's laws
- Friction is a force that opposes sliding between two surfaces.
G
- Gas pressureParticles and heat
- Gas particles hit the walls of their container, and the many tiny hits make pressure.
- Gravitational potential energyEnergy, work and power
- The energy stored in an object because of its height.
H
- Half-lifeAtoms and radioactivity
- The time taken for half of the unstable nuclei in a sample to decay.
I
- Ionising radiation and safetyAtoms and radioactivity
- Alpha, beta and gamma can knock electrons off atoms (ionisation), which can damage cells and cause cancer.
K
- Kinetic energyEnergy, work and power
- The energy of a moving object.
M
- Magnetic fieldsMains electricity and magnetism
- The region around a magnet where another magnet or a magnetic material feels a force.
- Mains electricityMains electricity and magnetism
- In the UK, mains electricity is alternating current (a.c.) at 230 V and 50 Hz.
- Motor effectMains electricity and magnetism
- A wire carrying current in a magnetic field feels a force.
N
- Newton's first lawForces and Newton's laws
- An object stays still or keeps moving at a steady speed in a straight line unless a resultant force acts on it.
- Newton's second lawForces and Newton's laws
- Resultant force = mass x acceleration (F = ma).
- Newton's third lawForces and Newton's laws
- When object A pushes on object B, B pushes back on A with an equal force in the opposite direction.
- Nuclear fissionAtoms and radioactivity
- A large nucleus, such as uranium-235, absorbs a neutron and splits into two smaller nuclei, releasing energy and more neutrons.
- Nuclear fusionAtoms and radioactivity
- Two small nuclei, such as hydrogen, join to make a larger nucleus and release energy.
O
- Ohm's lawElectric circuits
- V = I x R.
P
- Parallel circuitsElectric circuits
- Components on separate branches.
- Pitch and loudnessWaves, sound and light
- Pitch is how high or low a note sounds and depends on frequency.
- Plug wires and fusesMains electricity and magnetism
- A UK three-pin plug has a live wire (brown, carries the current), a neutral wire (blue, completes the circuit) and an earth wire (green and yellow, safety).
- Potential differenceElectric circuits
- The energy transferred per unit of charge as it moves between two points, measured in volts (V).
- PowerEnergy, work and power
- How fast energy is transferred.
R
- Radioactive decayAtoms and radioactivity
- An unstable nucleus randomly gives out radiation to become more stable.
- ReflectionWaves, sound and light
- A wave bounces off a surface.
- RefractionWaves, sound and light
- A wave changes speed, and usually direction, when it passes from one material into another.
- ResistanceElectric circuits
- How much a component opposes current, measured in ohms.
- Resultant forceForces and Newton's laws
- The single force that has the same effect as all the forces on an object added together, taking direction into account.
S
- Scalar and vectorMotion and measurement
- A scalar has size only, like 5 kg.
- Series circuitsElectric circuits
- Components in one single loop.
- SI unitsMotion and measurement
- The standard units scientists share worldwide: metre (m) for length, kilogram (kg) for mass and second (s) for time.
- SoundWaves, sound and light
- Sound is a longitudinal wave made by vibrations.
- Specific heat capacityParticles and heat
- The energy needed to raise the temperature of 1 kg of a substance by 1 degree C.
- SpeedMotion and measurement
- How far something travels each second.
- States of matterParticles and heat
- Solids, liquids and gases are three ways particles can be arranged.
- Static electricityMains electricity and magnetism
- Charge that builds up on an insulator when electrons are rubbed from one material to another.
- Structure of the atomAtoms and radioactivity
- An atom has a tiny nucleus of protons and neutrons, with electrons orbiting around it.
T
- Terminal velocityForces and Newton's laws
- The steady top speed reached when drag grows until it equals the driving force, so the resultant force is zero.
- Thermal radiationParticles and heat
- Heat that travels as infrared waves.
V
- VelocityMotion and measurement
- Speed in a stated direction.
- Velocity-time graphMotion and measurement
- A graph of velocity against time.
W
- Wave speed equationWaves, sound and light
- Wave speed = frequency x wavelength (v = f x lambda), measured in m/s.
- WavesWaves, sound and light
- A wave carries energy from place to place without carrying matter.
- Weight and massForces and Newton's laws
- Mass is the amount of matter in an object, in kg.
- Work doneEnergy, work and power
- Energy transferred when a force moves something.