A-Level Physics Terms

Front 1

a.c. generator

Back 1

A generator that, via the use of slip rings, produces an alternating e.m.f. and so an alternating current.

Front 2

absorption spectra

Back 2

A spectrum of dark line across the pattern of spectral colours produced when light passes through a gas and the gas absorbs certain frequencies, depending on the elements in the gas.

Front 3

acceleration (a)

Back 3

The rate of change of velocity, measured in ms⁻², a vector quantity.

Front 4

acceleration of free fall (g)

Back 4

The acceleration of a body falling under gravity.

Front 5

acoustic impedance (Z)

Back 5

The property of a material that determines the intensity of ultrasonic sound refracted at a boundary with another material. As given by Z = pc, measured in kg m⁻² s⁻¹

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activity (A)

Back 6

The number of radioactive decays per unit time. Measured in becquerels (Bq)

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alpha particle

Back 7

A particle comprising of 2 protons and 2 neutrons ejected from the nucleus during radioactive decay.

Front 8

alternating current

Back 8

Electric current that reverses it's direction with a constant frequency.

Front 9

ammeter

Back 9

A device used to measure electrical current, connected in series in a circuit.

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amount of substance

Back 10

SI quantity measured in moles (mol)

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ampere

Back 11

SI unit for electrical current

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amplitude, oscillations (X₀)

Back 12

The maximum displacement from the rest or equilibrium position, measured in metres (m)

Front 13

amplitude, waves (X₀)

Back 13

The maximum displacement of a wave from it's mean position, measured in metres (m)

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angular momentum

Back 14

A property of an object that depends on it's angular momentum.

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annihilation

Back 15

The process when a particle and an antiparticle interact and their combined mass is converted into energy via E = mc²

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antiparticle

Back 16

A particle of antimatter that has the same rest mass but, if charged, the equal and opposite charge to it's corresponding particle.

Front 17

area (A)

Back 17

A physical quantity representing the size of a surface, measured in metres squared (m²)

Front 18

astronomical unit (AU)

Back 18

The average distance from the earth to the sun. 1 AU = 1.496x10¹¹ m

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atom

Back 19

The smallest part of a specific element. It comprises protons, neutrons in the nucleus orbited by electrons.

Front 20

attenuation coefficient (µ)

Back 20

A constant used to calculate the intensity of x-rays as they pass through material.

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average speed

Back 21

A measure of the total distance traveled in a unit time.

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Avogadro constant (NA)

Back 22

A constant giving the number of particles in 1 mol of a substance. NA = 6.022x10²³ mol⁻¹

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baryon

Back 23

A particle consisting of 3 quarks

Front 24

baryon number

Back 24

A property of baryons and quarks that is conserved in particle interactions

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becquerel

Back 25

Unit of activity. Bq is 1 radioactive decay per second.

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beta decay

Back 26

The radio active decays which causes the emission of a beta particle and an anti neutrino from the nucleus when a neutron breaks down into a proton under the influence of a weak nuclear force.

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beta particle

Back 27

A high-speed electron emitted from the nucleus during beta decay.

Front 28

big bang theory

Back 28

The theory that the universe was made out of nothing from a single point. The universe was once much smaller, hotter and denser. It expended from that state to what we have today.

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binary stars

Back 29

Two stars in orbit about of common centre of gravity

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binding energy

Back 30

The energy required to separate an atom into it's component parts.

Front 31

binding energy per nucleon

Back 31

The average energy required to remove a nucleon from the nucleus

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black hole

Back 32

The remains of the core of a very large star after it has gone supernova. It has an infinite density and a gravitational field strength so great that even light cannot escape it.

Front 33

Boltzmann constant (k)

Back 33

A constant used when dealing with gases relating the temperature of the gas to the average kinetic energy of the particles in the gas. It can be thought of as a gas constant for a single molecule.

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bottom

Back 34

Type of quark

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Boyle's Law

Back 35

The volume of a fixed mass of gas is inversely proportional to pressure exerted on it provided the temperature remains constant.

Front 36

Brownian motion

Back 36

The random movement of small particles when suspended in a liquid or gas.

Front 37

Capacitance (C)

Back 37

The charge stored per unit potential difference, as given by C = Q/V. Measured in farads (F)

Front 38

Capacitor

Back 38

An electrical component designed to store charge.

Front 39

Capacitor Discharge

Back 39

Connecting a charged capacitor across a resistor and so enabling the charge to flow from one plate to another. The charge remaining decays exponentially, Q = Q₀e∧-t/CR

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Centre of Gravity

Back 40

The point at which the entire weight of an object can be considered to act.

Front 41

Centre of Mass

Back 41

Similar to centre to gravity, but is point that mass is considered to act.

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Centripetal Acceleration (a)

Back 42

The acceleration of a body moving in a circle with constant speed towards the centre of the circle. Given by a=v²/r, measured in ms⁻²

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Centripetal Force

Back 43

The resultant force on an object, acting towards the centre of the circle causing it to move in a circular path. Measured in N

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Chain Reaction

Back 44

One reaction causing another, which causes another, etc...

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Charm

Back 45

A type of quark

Front 46

Circular Motion

Back 46

When an object travels along a circular path, either in a complete circle or as part of a curve with a constant radius.

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Closed Universe

Back 47

The situation if the mean density of the universe is greater than the critical density. The universe will collapse back into a single point.

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Cloud Chamber

Back 48

A device used to detect charged particle by the formation of small clouds along trails of ions.

Front 49

Collimation

Back 49

Focusing an electromagnetic wave to provide parallel waves

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Comet

Back 50

A body comprising mainly of ice and rock in orbit around a star. These orbits are usually highly elliptical.

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Components of a Vector

Back 51

The results from resolving a single vector into horizontal and vertical parts.

Front 52

Compton Effect

Back 52

The effect whereby x-rays deflected off particles have a longer wavelength than their initial wavelength.

Front 53

Computerised Axial Tomograpthy (CAT)

Back 53

A process using X-rays in 3D and computers in order to produce an image of a slice through a body.

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Conductor

Back 54

A material with a high number density of conduction electrons and therefore a low resistor.

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Conservation of Charge

Back 55

Physical law stating charge is conserved in all interactions; it cannot be created or destroyed .

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Conservation of Energy

Back 56

Physical law stating energy cannot be created or destroyed, just transformed from one form to another, from one place to another. This is the situation in any closed circuit.

Front 57

Conservation of Momentum

Back 57

Physical law stating that in absence of external forces the total momentum of a system remains constant.

Front 58

Conventional Current

Back 58

A model used to describe the movement of charge in circuit. Conventional current travels from + to -

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Cosmological Principle

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On a large scale the universe is uniform

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Coulomb

Back 60

Unit of electrical charge (C), e.g. 1.6x10⁻¹⁹, 1C = 1A x 1s

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Coulomb's Law

Back 61

The force between two charges is proportional to the product of the charges and is inversely proportional to to the square of the distance between the charges.

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Couple

Back 62

Two forces acting together on an object that are equal and opposite to each other but not in the same straight line.

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Critical Damping

Back 63

The damping of an oscillating system when the forces cause the system to return to the equilibrium position without oscillating.

Front 64

Critical Density of the Universe (pc)

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The average density of the universe above which the universe will collapse (closed universe) and below which the universe will expand forever (open universe). pc = 9.5x10⁻²⁷ kg m⁻³

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Damped Oscillations

Back 65

Oscillations in which the kinetic energy is converted into other forms and so the amplitude of the oscillation reduces.

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de Broglie Equation

Back 66

An equation expressing the wavelength of a particle as a ratio of Planck's constant and the particle's momentum, mv.

Front 67

Decay Constant (λ)

Back 67

The probability of radioactive decay. Given by λ=A/N, measured in s⁻¹

Front 68

Degree Celsius

Back 68

Unit for tempreture

Front 69

density (p)

Back 69

The mass per unit volume, measured in kilograms per cubic metre (kg m⁻³) A scalar quantity.

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Diffraction

Back 70

Spreading of a wave after it passes around an obstacle or through a gap.

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Displacement (s or x)

Back 71

The distance traveled in a particular direction, measured in metres (m), e.g. 3m. A vector quantity.

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Displacement, s.h.m.

Back 72

The displacement of a body undergoing s.h.m. from the rest or equilibrium position. Given by x = x₀ sin (2πft). Measured in metres (m).

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Displacement-time Grath

Back 73

A motion graph showing the displacement against the time for a given body.

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Distance (d)

Back 74

How far one position is from another, measured in metres. A scalar quantity.

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Doppler effect

Back 75

The change in wavelength caused by the relative motion between the wave source and an observer.

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Down

Back 76

Type of quark

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Driving Force

Back 77

A force applied at regular intervals in order to keep an object oscillating.

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Dyanamo

Back 78

A device used to convert kinetic energy into electrical energy.

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Efficiency

Back 79

The ratio of useful output energy to total input energy.

Front 80

Einstein's mass/energy equation

Back 80

Equation linking energy, mass and the speed of light in a vacuum. E=mc²

Front 81

Elastic Collision

Back 81

In a perfectly elastic collision kinetic energy and momentum are conversed.

Front 82

Elastic potential energy

Back 82

The energy stored in a stretched or compressed object, measured in joules (J), a scalar quantity.

Front 83

Electrical Charge (Q or q) = current x time

Back 83

Measured in coulombs (C) a scalar quantity.

Front 84

Electrical Current (I)

Back 84

A flow of charge. A vector quantity, measured in amperes (A)

Front 85

Electrical Fields

Back 85

A region of space where a charged particle experiences a force. It goes from + to -

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Electrical Field Strength (E)

Back 86

Force per unit positive charge, given by E =F/q, measured in N C⁻¹

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Electromagnetic Induction

Back 87

The process of inducing an e.m.f. using a magnetic field and a changing flux linkage.

Front 88

Electromagnetic Wave

Back 88

A self-propagating transverse wave that does not require a medium to travel through.

Front 89

Electromotive Force (e.m.f.)

Back 89

The electrical energy transferred per unit charge when one form of energy is converted into electrical energy, measured in volts (V).

Front 90

electron

Back 90

Negatively charged sub-atomic particle with a charge of 1.6x10⁻¹⁹C. Conduction electrons travel around circuits creating an electric current. A lepton.

Front 91

Electron Diffraction

Back 91

The process of diffracting an electron through a gap (usually between atoms in a crystal structure, for example graphite). An example of wave-particle duality.

Front 92

Electron Flow

Back 92

The movement of electrons (usually around a circuit), from - to +.

Front 93

Electron Volt

Back 93

One electron volt is the energy change of an electron when it moves through a potential difference of one volt. It's value is 1.6x10⁻¹⁹

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Emission Spectrum

Back 94

A pattern of colours of light emitted by a substance with specific wavelengths.

Front 95

Endoscope

Back 95

A coated bundle of optic fibres inserted into the body to provide an image of the internal organs without the need for evasive surgery.

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Energy (E)

Back 96

The stored ability to do work, measured in joules (J), a scalar quantity.

Front 97

Energy Levels

Back 97

One of the specific energies an electron can have when in an atom.

Front 98

Equations of Motion

Back 98

The equations used to describe displacement, acceleration, initial velocity, final velocity and time when a body under goes a constant acceleration.

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Equilibrium

Back 99

The state when zero resultant force acts on an object.

Front 100

Exponential Decay

Back 100

At any given time interval there is the same ratio of constant value to starting value. For example, capacitor discharge, or radioactive decay.

Front 101

Farad

Back 101

Unit of Capacitance (F). 1 F is 1C of charge stored per volt.

Front 102

Faraday's Law

Back 102

The magnitude of the induced e.m.f. is equal to the rate of change of flux linkage.

Front 103

Field

Back 103

A region in which a force operates.

Front 104

Fission

Back 104

The process of splitting a large nucleus into two smaller nuclides, often with the emission of several neutrons. This releases energy because of the change in binding energy.

Front 105

Fission Products

Back 105

The particles and energy released when a nucleus undergoes nuclear fission.

Front 106

Flat Universe

Back 106

The situation if the mean density of the universe is equal to the critical density. The galaxies in the universe will slow down but never quite stop. This situation is very unlikely.

Front 107

Fleming's left-hand rule

Back 107

Used with electric motors and forces acting on moving charges in magnetic fields. It shows the direction of the force on a conductor carrying a current in a magnetic field. Force = Thumb, Field = Index Finger, Current = Middle Finger, all at right angles to one another.

Front 108

Fleming's right-hand rule

Back 108

Used with generators and electromagnetic induction. It shows the direction of the induced current when a conductor moves through a magnetic field. Force = Thumb, Field = Index Finger, Current = Middle Finger, all at right angles to one another.