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AQA A-Level Physics > Definitions > Flashcards

Flashcards in Definitions Deck (100)
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1
Q

Vector

A

A physical quantity with magnitude and direction

2
Q

Scalar

A

A physical quantity with magnitude only

3
Q

Moment

A

Force times perpendicular distance from the line of action of the force to the point

4
Q

Principle of moments

A

For an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments about any point

5
Q

Couple

A

A pair of equal and opposite forces acting on a body, but not along the same line

6
Q

Velocity

A

Change of displacement per unit time

7
Q

Acceleration

A

Change of velocity per unit time

8
Q

Newton’s 1st Law

A

An object will remain at rest or at a constant velocity unless acted on by an external resultant force

9
Q

Newton’s 2nd Law

A

The force is proportional to the rate of change of momentum

10
Q

Newton’s 3rd Law

A

For every action there is an equal and opposite reaction

11
Q

Equilibrium

A

State of an object when at rest or moving at constant velocity

12
Q

Density

A

Mass per unit volume of the substance

13
Q

Stress

A

Force per unit area of cross section in a solid perpendicular to the cross section

14
Q

Strain

A

Extension per unit length of a solid when deformed

15
Q

Young’s Modulus

A

Tensile stress/strain

16
Q

Limit of Proportionality

A

The limit beyond which, when a wire or a spring is stretched, its extension is no longer proportional to the force that stretches it

17
Q

Plastic deformation

A

Deformation of a solid beyond its elastic limit

18
Q

Elastic limit

A

Point beyond which a wire is permanently stretched

19
Q

Hooke’s Law

A

The extension of a spring is directily proportional to the force applied to it, up to the limit of proportionality

20
Q

Isotope

A

Atoms with the same number of protons but different numbers of neutrons

21
Q

Conservation of energy

A

Energy cannot be created or destroyed, only converted from one form to another

22
Q

Work done

A

Force times distance moved in the direction of the force

23
Q

Ductile

A

Material that can be drwan into threads, it can be shaped or permanently deformed without fracture

24
Q

Brittle

A

Material cannot be permanently stretched

25
Q

Wave

A

Transfer energy from A to B via a medium of transfer, without transferring the medium

26
Q

Standing wave

A

When two waves travel in opposing directions and they have the same wave speed, frequency and in general amplitude, they will superpose and form a standing wave

27
Q

Monochromatic

A

Single wavelength

28
Q

Coherent

A

No change in phase relationship

29
Q

Collimated

A

Formed in a narrow beam

30
Q

Diffraction

A

Spreading out or bending of waves as they pass through a gap or around an obstacle

31
Q

Emf

A

Describes the amount of energy that is converted from one form to electrical and placed on a unit of charge at the source

32
Q

Ohm’s Law

A

The current flowing through a metallic conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant

33
Q

Resistivity

A

The resistance of a piece of wire 1m in length and with a cross sectional area of 1m^2

34
Q

Centre of mass

A

The point through which a single force on the body has no turning effect

35
Q

Principle of conservation of linear momentum

A

The total linear momentum of a system of interacting bodies is constant, providing no external forces act

36
Q

Work function

A

Minimum energy to liberate electron

37
Q

Excitation

A

When an electrion takes in energy from a photon or collision and goes up an energy level

38
Q

Ionisation

A

When an electron takes in enough energy to leave the atom

39
Q

Motive power

A

Power outputted by a powered object (i.e. engine or muscle)

40
Q

Progressive waves

A

Waves that move outwards from their source

41
Q

Transverse waves

A

Each particle oscillates perpendicular to the direction of propagation to the wave

42
Q

Longitudinal wves

A

Each particle oscillates parallel to the direction of propagation to the wave

43
Q

Rarefied

A

More distance between particles than usual

44
Q

Compression

A

Particles closer together

45
Q

Mechanical waves

A

Oscillation of particles in a physical medium

46
Q

Electromagnetic waves

A

Acceleration of charged particles, and can transmit energy through a vacuum

47
Q

Refraction

A

Change in path of light ray caused by a change in speed

48
Q

Total internal reflection

A

The angle of incidence is greater than the critical angle

49
Q

Diffraction

A

The spreading of waves when passed through a gap or round an obstacle

50
Q

Kirchhoff’s First Law

A

The sum of the currents leaving any junction is always equal to the sum of the currents that entered it

51
Q

Kirchhoff’s Second Law

A

The sum of potential differences across components of a series circuit is equal to the emf

52
Q

Internal Resistance

A

Resistance inside a source of electrical energy; the loss of pd per unit current in the source when current passes through it

53
Q

Potential Divider

A

Two or more resistors in series connected to a source of pd

54
Q

Superconductor

A

A material that has zero electrical resistance

55
Q

Gravitational Field Strength

A

The force per unit mass acting on a small test mass placed in the field

56
Q

Gravitational Potential

A

The work done to move a small object from infinity to that point in a gravitational field

57
Q

Kepler’s First Law

A

All planets move about the Sun in elliptical orbits, having the Sun as one of the foci

58
Q

Kepler’s Second Law

A

A radius vector joining any planet to the sun, sweeps out equal areas in equal lengths of time

59
Q

Kepler’s Third Law

A

The square of the period of a planet’s orbit is proportional to the cube of the mean radius of its orbit

60
Q

Coulomb’s Law

A

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

61
Q

Electric Field

A

Region where a charged particle will experience a force

62
Q

Gravitational Field

A

The region surrounding an object in which it exerts a gravitational force on any other object

63
Q

Geostationary Satellite

A

A satellite that stays above the same point on the Earth’s equator as it’s period is 24 hours and has the same rotation direction

64
Q

Electric Field Strength

A

Force per unit charge acting on a small positive test charge at a point in the field

65
Q

Potential Gradient

A

Change of potential per metre at a point in a gravitational field

66
Q

Electric Potential

A

Work done per unit positive charge moving a small positive charge from infinity to that point in the field

67
Q

Field

A

A region around an object where a force is exerted

68
Q

Capacitance

A

The charge stored per unit pd of a capacitor

69
Q

Dielectric

A

Material that increases the capacity of a parallel-plate capacitor to store charge when placed between the plates of the capacitor

70
Q

Activity

A

The number of unstable radioactive nuclei that decay per second

71
Q

Metastable State

A

An excited state of the nuclei of an isotope that last long enough after α or β emission for the isotope to be separated from the parent isotope

72
Q

Atomic Mass Unit

A

One twelfth of the mass of a carbon-12 atom

73
Q

Mass Defect

A

Mass of separated nucleons minus mass of nucleus

74
Q

Binding Energy

A

The work that must be done to separate a nucleus into its constituent nucleons

75
Q

Critical Mass

A

The minimum mass required to sustain a chain reaction of fission in a nuclear reactor

76
Q

Fuel Rods (Nuclear Reactor)

A

Contains enriched uranium. Increased % of U-235 compared to uranium ore it’s extracted from

77
Q

Control Rods (Nuclear Reactor)

A

Made of cadmium or boron to absorb neutrons

Lifted in and out of the reactor to control the number of neutrons present and the rate of fission

78
Q

Moderator (Nuclear Reactor)

A

Made of graphite or water

Slows down fission neutrons into one thermal energies, to increase the likelihood of absorption by U-235 nuclei

79
Q

Coolant (Nuclear Reactor)

A

Water flows around the core, transferring heat away from the fuel, to be used to produce steam to drive a turbine

80
Q

Angular Displacement

A

The angle moved through relative to a specific axis

81
Q

Angular Velocity

A

The rate of change of angular displacement with respect to time

82
Q

Centripetal Force

A

The force that makes an object move in a circle

83
Q

Simple Harmonic Motion

A

Acceleration is proportional to the displacement of the object from equilibrium and is always directed towards the equilibrium position

84
Q

Natural Frequency

A

The frequency of free oscillations of an oscillating system

85
Q

Free Vibrations

A

Vibrations where there is no damping and no periodic force acting on the system, so the amplitude of the oscillations is constant

86
Q

Forced Vibrations

A

Vibrations of a system subjected to an external periodic force

87
Q

Resonance

A

The driving force matches the natural frequency of the system, leading to an increased amplitude of oscillation

88
Q

Damping

A

The removal of energy from an oscillating system

89
Q

Magnetic Flux Density

A

The magnetic force per unit length per unit current on a current carrying conductor at right angles to the field lines

90
Q

Electromagnetic Induction

A

The generation of an emf when the magnetic flux linkage through a coil changes or a conductor cuts across magnetic field lines

91
Q

Lenz’s Law

A

The direction of the induced emf is always such as to oppose the change that causes the emf

92
Q

Hall Probe

A

A device used to measure magnetic flux density

93
Q

Magnetic Flux

A

The product of magnetic flux density and the area perpendicular to the field

94
Q

Magnetic Flux Linkage

A

A measure of the magnetic flux of a coil of wire

95
Q

Faraday’s Law of Electromagnetic Induction

A

The induced emf in a circuit is equal to the rate of change of magnetic flux linkage through the circuit

96
Q

Eddy Current

A

Induced currents in the metal parts of ac machines

97
Q

Internal Energy

A

Sum of Ep and Ek of molecules within the body

98
Q

Boyle’s Law

A

When a fixed mass of gas is reduced in volume by a compressing piston, the pressure inside the piston increases

99
Q

Charles’ Law

A

For the fixed mass of an ideal gas at constant pressure, its volume is directly proportional to its absolute temperature

100
Q

Ideal Gas

A

A gas under conditions such that it obeys Boyle’s Law