Word Definitions

Question 1

Absolute Zero

Answer 1

The lowest possible temperature of a system, where no heat

remains and the particles in the system have no kinetic energy.

Question 2

Boltzmann Constant

Answer 2

: A constant relating the average kinetic energy of the

particles in a gas, to the gas’ temperature.

Question 3

Boyle’s Law

Answer 3

The pressure of an ideal gas is inversely proportional to its volume
when held at constant temperature.

Question 4

Brownian Motion

Answer 4

The random motion of particles.

Question 5

Charles’ Law

Answer 5

The volume of an ideal gas is directly proportional to its absolute
temperature when held at constant pressure.

Question 6

Ideal Gas

Answer 6

A gas that meets the ideal gas assumptions. All the gas laws are
based on ideal gases.

Question 7

Internal Energy

Answer 7

The sum of the randomly distributed kinetic and potential

energies of the particles in a given system.

Question 8

Pressure Law

Answer 8

The pressure of an ideal gas is directly proportional to its absolute
temperature, when the volume is fixed.

Question 9

Back Emf

Answer 9

An emf generated by the coil in an AC generator that acts against the
potential difference that has been supplied to the motor.

Question 10

Capacitance, C

Answer 10

Capacitance, C: The charge stored per unit pd in a capacitor.

Question 11

Dielectric

Answer 11

Dielectric: An insulating material placed between the two plates of a capacitor in
order to increase the amount of charge it can store.

Question 12

Electric Field

Answer 12

A region surrounding a charged object which causes a force to be
exerted on any charged object placed within the field.

Question 13

Electromagnetic Induction

Answer 13

When an emf is induced in a wire/conducting rod

when it is moved relative to a magnetic field.

Question 14

Equipotential

Answer 14

A surface of constant potential. No work is done by the field when an object
moves along an equipotential.

Question 15

Faraday’s Law

Answer 15

The magnitude of the induced emf is equal to the rate of change
of flux linkage through the circuit.

Question 16

Geostationary Satellite

Answer 16

Geostationary Satellite: A satellite that orbits above the equator with a 24 hour period, so it
will always remain above the same position on the Earth. They orbit approximately 36,000km
above the surface of the Earth

Question 17

Kepler’s Third Law:

.

Answer 17

Kepler’s Third Law: The square of an object’s orbital period (T) is directly proportional to the
cube of its orbital radius (r) – T^2 ∝ r^3

Question 18

Lenz’s Law

Answer 18

An induced current is always in a direction so as to oppose the
change that caused it.

Question 19

Magnetic Flux, ϕ:

Answer 19

Magnetic Flux, ϕ: A value which describes the magnetic field or field lines passing through
an area. It is the product of magnetic flux density and the perpendicular area it passes
through.

Question 20

Magnetic Flux Density, B

Answer 20

Magnetic Flux Density, B: The force per unit current per unit length on a current-carrying
wire placed at 90º to the field lines. Sometimes also referred to as the magnetic field
strength.

Question 21

Magnetic Flux Linkage, Nϕ:

Answer 21

Magnetic Flux Linkage, Nϕ: The magnetic flux multiplied by the number of turns, N, of the
coil.

Question 22

Motor Effect

Answer 22

When a current-carrying wire is placed within a magnetic field
(non-parallel to the field lines) and experiences a force perpendicular to both the
wire and the field lines.

Question 23

Permittivity of free space, ε0

Answer 23

A measure of the ability of a vacuum to allow an electric field
to pass through it

Question 24

Polarised

Answer 24

An atom/molecule becomes polarised when an external electric field causes the
negative electron cloud to be shifted in the opposite direction to the positive nucleus – the
charges are pulled in opposite directions. (This is what happens to the molecules of the
dielectric in a capacitor).

Question 25

Potential Gradient

Answer 25

Potential Gradient: The change of potential per metre at a point in the field.

Question 26

Radial Field

Answer 26

Radial Field: A field in which the field lines are all directed towards a single point (e.g. the
centre of a planet or a point charge).

Question 27

Relative Permittivity

Answer 27

Relative Permittivity: The ratio of charge stored in a capacitor with the dielectric to charge
stored without the dielectric. Also sometimes referred to as the dielectric constant

Question 28

Activity

Answer 28

The rate of decay of the radioactive nuclei in a given isotope. It is
proportional to the total number of nuclei in the sample and is measured in
Becquerels.

Question 29

Atomic Mass Unit

Answer 29

A unit used to express atomic masses. One AMU is equal to

the one twelfth of the mass of a carbon atom.

Question 30

Background Radiation

Answer 30

Radiation that is found in small quantities all around us. It
originates from natural sources such as rocks and cosmic rays as well as
man-made sources such as nuclear accidents and medical sources.

Question 31

Binding Energy

Answer 31

The amount of energy required to split a nucleus into all its
separate constituent nucleons. It is equivalent to the mass defect.

Question 32

Closest Approach

Answer 32

A method of estimating a nuclear radius by firing a alpha
particle at it. It involves calculating the distance at which all the alpha particle’s
kinetic energy is converted to electric potential energy.

Question 33

Coolant

Answer 33

A substance that passes through nuclear reactors and is responsible for
removing heat from the core. This heat is then used to generate energy.

Question 34

Critical Mass

Answer 34

The smallest mass of fissile material required in a fission reactor
for a chain reaction to be sustained.

Question 35

Inverse Square-Law

Answer 35

Inverse Square-Law: A law that governs the intensity of gamma radiation. It
means that the intensity of radiation at any point is inversely proportional to the
square of the distance from its source.

Question 36

Irradiation

Answer 36

Irradiation: The exposure of an object to radiation. The exposed object does not
become radioactive.

Question 37

Moderator

Answer 37

A material in nuclear reactors that absorbs energy from fast moving
neutrons, to slow them down to speeds that can be absorbed by fissile neutrons to
induce fission.

Question 38

Radioactive Dating

Answer 38

The use of radioactive isotopes with known half-lives to date
objects. The isotope that is usually used is Carbon-14.