A LEVEL PHYSICS AQA DEFINITIONS(LATEST
2025/2026) STUDY GUIDE WITH COMPLETE
SOLUTIONS
Absolute Zero - ✔✔ANSWER✔✔->>Lowest possible temperature, 0K, object has
minimum internal energy.
Acceleration - ✔✔ANSWER✔✔->>Change of velocity per unit time.
Activity of a Radioactive Isotope - ✔✔ANSWER✔✔->>Number of nuclei of the
isotope that disintegrate per second.
Becquerel (Bq) - ✔✔ANSWER✔✔->>Unit of radioactive activity, 1Bq = 1
disintegration per second.
Amplitude - ✔✔ANSWER✔✔->>Maximum displacement from equilibrium of
oscillating object.
,Angular Displacement - ✔✔ANSWER✔✔->>Angle an object in circular motion
turns through in radians.
𝜃 = 𝜔t
Angular Speed (ω) - ✔✔ANSWER✔✔->>Rate of change of angular displacement of
object in circular motion.
𝜔 = 2𝜋f
Annihilation - ✔✔ANSWER✔✔->>When a *particle and its antiparticle meet*,
they destroy each other to *produce 2 photons of equal energy*.
Here the minimum energy of each photon produced = hf(min) = rest energy of the
particle.
Antiparticle - ✔✔ANSWER✔✔->>*Equal rest mass* and *equal and opposite
charge* to particle.
Atomic Number, Z - ✔✔ANSWER✔✔->>Number of *protons* in nucleus of atom.
Avogadro Constant - ✔✔ANSWER✔✔->>The *number of atoms in 12g of carbon-
12*. Used to define the mole.
Back emf - ✔✔ANSWER✔✔->>The emf induced in the spinning coil of electric
motor or in any coil in which the current is changing. A back emf acts against the
change of applied pd.
,Background Radiation - ✔✔ANSWER✔✔->>*Radiation due to naturally occurring
substances* in the environment e.g. radon gas, cosmic rays, ground and buildings.
Binding Energy - ✔✔ANSWER✔✔->>*Work done* to separate a nucleus into its
*constituent nucleons* (neutrons and protons).
E = mass defect x c²
Binding Energy per Nucleon - ✔✔ANSWER✔✔->>Average work done per nucleon
to separate nucleus into constituent parts. Higher the value, the more stable the
nucleus.
*BE per nucleon = BE of a nucleus / mass number*.
Boyle's Law - ✔✔ANSWER✔✔->>For a *fixed mass of gas* at a *constant
temperature*, its *pressure x volume is constant*. Gases that obey this are an
ideal gas.
Boltzmann Constant (k) - ✔✔ANSWER✔✔->>Molar gas constant divided by
Avogadro number.
Brittle - ✔✔ANSWER✔✔->>Snaps without stretching or bending when subject to
stress.
Brownian Motion - ✔✔ANSWER✔✔->>*Random and unpredictable motion of a
particle* eg. smoke particles caused by molecules of the surrounding substance
colliding with it. Provided evidence for existence of atom.
, Capacitance - ✔✔ANSWER✔✔->>The *charge stored per unit pd of a capacitor*.
Unit is Farad (F) equal to 1 coulomb per volt. Q = CV.
Centre of Mass - ✔✔ANSWER✔✔->>Point through which a single force on the
body has no turning effect.
Centripetal Force - ✔✔ANSWER✔✔->>Resultant force on an object that moves
along a circular path. Acts towards centre of circle.
F = mv²/r = m𝜔²r
Chain Reaction - ✔✔ANSWER✔✔->>Series of reactions in which each reaction
causes a further reaction e.g. nuclear fission. Steady reaction where on average
one neutron from each fission event goes on to cause a further fission event.
Charge Carriers - ✔✔ANSWER✔✔->>Charged particles that move through a
substance when a pd is applied across it.
Charles' Law - ✔✔ANSWER✔✔->>For a *fixed mass* of an ideal gas at a *constant
pressure*, volume is directly proportional to its absolute temperature
Coherent - ✔✔ANSWER✔✔->>Two sources of waves emitted with a constant
phase difference.
Conservation of Momentum - ✔✔ANSWER✔✔->>Total momentum of objects in
system remains constant provided no external force acts on system.
2025/2026) STUDY GUIDE WITH COMPLETE
SOLUTIONS
Absolute Zero - ✔✔ANSWER✔✔->>Lowest possible temperature, 0K, object has
minimum internal energy.
Acceleration - ✔✔ANSWER✔✔->>Change of velocity per unit time.
Activity of a Radioactive Isotope - ✔✔ANSWER✔✔->>Number of nuclei of the
isotope that disintegrate per second.
Becquerel (Bq) - ✔✔ANSWER✔✔->>Unit of radioactive activity, 1Bq = 1
disintegration per second.
Amplitude - ✔✔ANSWER✔✔->>Maximum displacement from equilibrium of
oscillating object.
,Angular Displacement - ✔✔ANSWER✔✔->>Angle an object in circular motion
turns through in radians.
𝜃 = 𝜔t
Angular Speed (ω) - ✔✔ANSWER✔✔->>Rate of change of angular displacement of
object in circular motion.
𝜔 = 2𝜋f
Annihilation - ✔✔ANSWER✔✔->>When a *particle and its antiparticle meet*,
they destroy each other to *produce 2 photons of equal energy*.
Here the minimum energy of each photon produced = hf(min) = rest energy of the
particle.
Antiparticle - ✔✔ANSWER✔✔->>*Equal rest mass* and *equal and opposite
charge* to particle.
Atomic Number, Z - ✔✔ANSWER✔✔->>Number of *protons* in nucleus of atom.
Avogadro Constant - ✔✔ANSWER✔✔->>The *number of atoms in 12g of carbon-
12*. Used to define the mole.
Back emf - ✔✔ANSWER✔✔->>The emf induced in the spinning coil of electric
motor or in any coil in which the current is changing. A back emf acts against the
change of applied pd.
,Background Radiation - ✔✔ANSWER✔✔->>*Radiation due to naturally occurring
substances* in the environment e.g. radon gas, cosmic rays, ground and buildings.
Binding Energy - ✔✔ANSWER✔✔->>*Work done* to separate a nucleus into its
*constituent nucleons* (neutrons and protons).
E = mass defect x c²
Binding Energy per Nucleon - ✔✔ANSWER✔✔->>Average work done per nucleon
to separate nucleus into constituent parts. Higher the value, the more stable the
nucleus.
*BE per nucleon = BE of a nucleus / mass number*.
Boyle's Law - ✔✔ANSWER✔✔->>For a *fixed mass of gas* at a *constant
temperature*, its *pressure x volume is constant*. Gases that obey this are an
ideal gas.
Boltzmann Constant (k) - ✔✔ANSWER✔✔->>Molar gas constant divided by
Avogadro number.
Brittle - ✔✔ANSWER✔✔->>Snaps without stretching or bending when subject to
stress.
Brownian Motion - ✔✔ANSWER✔✔->>*Random and unpredictable motion of a
particle* eg. smoke particles caused by molecules of the surrounding substance
colliding with it. Provided evidence for existence of atom.
, Capacitance - ✔✔ANSWER✔✔->>The *charge stored per unit pd of a capacitor*.
Unit is Farad (F) equal to 1 coulomb per volt. Q = CV.
Centre of Mass - ✔✔ANSWER✔✔->>Point through which a single force on the
body has no turning effect.
Centripetal Force - ✔✔ANSWER✔✔->>Resultant force on an object that moves
along a circular path. Acts towards centre of circle.
F = mv²/r = m𝜔²r
Chain Reaction - ✔✔ANSWER✔✔->>Series of reactions in which each reaction
causes a further reaction e.g. nuclear fission. Steady reaction where on average
one neutron from each fission event goes on to cause a further fission event.
Charge Carriers - ✔✔ANSWER✔✔->>Charged particles that move through a
substance when a pd is applied across it.
Charles' Law - ✔✔ANSWER✔✔->>For a *fixed mass* of an ideal gas at a *constant
pressure*, volume is directly proportional to its absolute temperature
Coherent - ✔✔ANSWER✔✔->>Two sources of waves emitted with a constant
phase difference.
Conservation of Momentum - ✔✔ANSWER✔✔->>Total momentum of objects in
system remains constant provided no external force acts on system.
