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A Level Physics MASTER > Definitions > Flashcards

Definitions Flashcards

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1
Q

Vector

A

A physical quantity with magnitude and direction

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2
Q

Scalar

A

A physical quantity with magnitude only

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3
Q

Moment

A

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

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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

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5
Q

Couple

A

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

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6
Q

Velocity

A

Change of displacement per unit time

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7
Q

Acceleration

A

Change of velocity per unit time

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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

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9
Q

Newton’s 2nd Law

A

The force is proportional to the rate of change of momentum

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10
Q

Newton’s 3rd Law

A

For every action there is an equal and opposite reaction

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11
Q

Equilibrium

A

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

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12
Q

Density

A

Mass per unit volume of the substance

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13
Q

Stress

A

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

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14
Q

Strain

A

Extension per unit length of a solid when deformed

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15
Q

Young’s Modulus

A

Tensile stress/strain

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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

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17
Q

Plastic deformation

A

Deformation of a solid beyond its elastic limit, the object will not return to its original length once the force is removed.

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18
Q

Elastic limit

A

Point beyond which a wire is permanently stretched

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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

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20
Q

Isotope

A

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

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21
Q

Conservation of energy

A

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

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22
Q

Work done

A

Force times distance moved in the direction of the force

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23
Q

Ductile

A

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

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24
Q

Brittle

A

Material cannot be permanently stretched

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25
Q

Wave

A

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

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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

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27
Q

Monochromatic

A

Single wavelength

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28
Q

Coherent

A

No change in phase relationship

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29
Q

Diffraction

A

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

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30
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

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31
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

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32
Q

Resistivity

A

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

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33
Q

Centre of mass

A

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

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34
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

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35
Q

Work function

A

Minimum energy to liberate electron

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36
Q

Excitation

A

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

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37
Q

Ionisation

A

When an electron takes in enough energy to leave the atom

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38
Q

Progressive waves

A

Waves that move outwards from their source

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39
Q

Transverse waves

A

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

40
Q

Longitudinal wves

A

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

41
Q

Rarefied

A

More distance between particles than usual

42
Q

Compression

A

Particles closer together

43
Q

Mechanical waves

A

Oscillation of particles in a physical medium

44
Q

Refraction

A

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

45
Q

Total internal reflection

A

The angle of incidence is greater than the critical angle

46
Q

Diffraction

A

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

47
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

48
Q

Kirchhoff’s Second Law

A

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

49
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

50
Q

Potential Divider

A

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

51
Q

Superconductor

A

A material that has zero electrical resistance below a critical temperature.

52
Q

Gravitational Field Strength

A

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

53
Q

Gravitational Potential

A

The work done to move a unit mass from infinity to that point in a gravitational field

54
Q

Kepler’s First Law

A

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

55
Q

Kepler’s Second Law

A

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

56
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

57
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

58
Q

Electric Field

A

Region where a charged particle will experience a force

59
Q

Gravitational Field

A

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

60
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

61
Q

Electric Field Strength

A

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

62
Q

Electric Potential

A

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

63
Q

Field

A

A region around an object where a force is exerted

64
Q

Capacitance

A

The charge stored per unit pd of a capacitor

65
Q

Dielectric

A

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

66
Q

Activity

A

The number of unstable radioactive nuclei that decay per second

67
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

68
Q

Atomic Mass Unit

A

One twelfth of the mass of a carbon-12 atom

69
Q

Mass Defect

A

Mass of separated nucleons minus mass of nucleus

70
Q

Binding Energy

A

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

71
Q

Critical Mass

A

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

72
Q

Fuel Rods (Nuclear Reactor)

A

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

73
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

74
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

75
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

76
Q

Angular Displacement

A

The angle moved through relative to a specific axis

77
Q

Angular Velocity

A

The rate of change of angular displacement with respect to time

78
Q

Centripetal Force

A

The force that makes an object move in a circle

79
Q

Simple Harmonic Motion

A

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

80
Q

Natural Frequency

A

The frequency of free oscillations of an oscillating system

81
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

82
Q

Forced Vibrations

A

Vibrations of a system subjected to an external periodic force

83
Q

Resonance

A

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

84
Q

Damping

A

The removal of energy from an oscillating system

85
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

86
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

87
Q

Lenz’s Law

A

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

88
Q

Hall Probe

A

A device used to measure magnetic flux density

89
Q

Magnetic Flux

A

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

90
Q

Magnetic Flux Linkage

A

A measure of the magnetic flux of a coil of wire

91
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

92
Q

Eddy Current

A

Induced currents in the metal parts of machines

93
Q

Internal Energy

A

Sum of Ep and Ek of molecules within the body

94
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

95
Q

Charles’ Law

A

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

96
Q

Ideal Gas

A

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

A Level Physics MASTER (17 decks)

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