Physics Keywords Flashcards
1
Q
Oscillate
A
To move to and fro about a certain position along a line (vibrate).
2
Q
Angle of incidence
A
The angle between the incidence (incoming) ray and the normal.
3
Q
Beta radiation
A
Beta particles, high energy electrons created in, and emitted from unstable nuclei.
4
Q
Boiling point
A
The temperature at which a pure substances boils or condenses.
5
Q
Split-ring communicator
A
Metal contacts on the coil of a direct current motor that connects the rotating coil continuously to its electrical power supply.
6
Q
Alpha radiation
A
Alpha particles, each containing two protons and two neutrons, emitted by unstable nuclei. Also referred to as a helium nucleus.
7
Q
Ohm’s law
A
The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor.
8
Q
Momentum
A
This equals mass (in kg) x velocity (in m/s).
9
Q
Transmission
A
A wave passing through a substance.
10
Q
Thermal conductivity
A
The property of a material that determines the energy transfer through it by conduction.
11
Q
Internal energy
A
The energy of the particles within a substance due to their individual motion and positions.
12
Q
Nuclear fusion
A
The process where small nuclei are fused together to form a larger nucleus.
13
Q
Magnification
A
The image height ÷ the object height
14
Q
Magnetic field line
A
Line in a magnetic field along which a magnetic compass points - also called a line of force.
15
Q
Specific latent heat of fusion
A
The energy needed to melt 1 kg of a substance with no change of temperature.
16
Q
Errors
A
In readings, measurements or results. Also known as uncertainties.
17
Q
Work
A
The energy transferred by a force. Work done (Joules, J) = force (Newtons, N) x distance moved in the direction of the force (metres, m)
18
Q
Weight
A
The force of gravity on an object (in Newtons, N).
19
Q
Compression
A
Squeezing or pressing together.
20
Q
White light
A
Light that includes all the colours of the visible spectrum.
21
Q
Red giant
A
A star that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.
22
Q
Longitudinal waves
A
Waves in which the vibrations are parallel to the direction of energy transfer. The wave direction is the same as the oscillations.
23
Q
Step-up transformer
A
An electrical device that is used to step-up (increase) the size of an alternating potential difference.
24
Q
Parallel (circuit)
A
Components connected in a circuit so that the potential difference across each is the same.
25
Alternating current (A.C.)
An electrical current in a circuit that repeatedly reverses its direction.
26
Gamma radiation
Electromagnetic radiation emitted from unstable nuclei in radioactive substances.
27
Infra-red radiation
Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum.
28
Driving force
The force of a vehicle that makes it move (also called motive force or thrust).
29
Induced magnetism
Magnetisation of an unmagnetised magnetic material by placing it in a magnetic field.
30
Generator effect
The production of a potential difference using a magnetic field.
31
Inverse proportionality
This is where two variables are related such that making one variable n times bigger, causes the other to become n times smaller (e.g. doubling one quantity causes the other to halve).
32
Risk
The likelihood that a hazard will actually cause harm.
33
S-wave Secondary seismic wave
Transverse waves that shake the Earth from side to side as they pass through.
34
Count rate
The number of counts per second detected by a Geiger counter.
35
Inertia
The tendency of an object to stay at rest or to continue in a uniform motion.
36
Latent heat
The energy transferred to or from a substance when it changes its state.
37
Angle of reflection
The angle between the reflected (outgoing) ray and the normal.
38
Atomic number
The number of protons (which equals the number of electrons) in an atom. Also called the proton number.
39
Scalar
A physical quantity, such as mass or energy, that has a magnitude only (unlike a vector which has magnitude and direction).
40
Concave (diverging) lens
A lens that makes parallel rays diverge (spread out).
41
Newton's third law of motion
When two objects interact with each other, they exert equal and opposite forces on each other.
42
Effort
The force applied to a device, used to raise a weight or move an object.
43
Nuclear fission
The process in which certain, large nuclei (uranium-235 and plutonium-239) are spilt into two fragments, releasing energy and two or three more neutrons as a result.
44
Protostar
The concentration of dust clouds and gas in space that forms a star.
45
Reflection
The change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium.
46
Renewable energy
Energy from natural sources that is always being replenished so that it will never run out.
47
Dissipation of energy
The energy that is not usefully transferred or stored. Transferred to less useful forms e.g. thermal energy.
48
Earth wire
The wire in a mains cable used to connect the metal case of an appliance to earth.
49
Supernova
The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses on to the core and rebounds.
50
Limit of proportionality
The limit for Hooke’s law applied to the extension of a stretched spring.
51
Redshift
The increase in the wavelength of electromagnetic waves emitted by a star or galaxy due to its motion away from us. The faster the speed of the star or galaxy, the greater the redshift is.
52
Neutrons
Uncharged particles of the same mass as protons. The nucleus of an atom consists of protons and neutrons.
53
Series (circuit)
Components connected in a circuit in such a way that the same current passes through each of them.
54
Hooke’s law
The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded.
55
Extension
The increase in length of a spring (or material) from its original length.
56
Motor effect
When a current is passed along a wire in a magnetic field, and the wire is not parallel to the lines of the magnetic field, a force is exerted on the wire by the magnetic field.
57
Red supergiant
A star much more massive than our Sun that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.
58
Directly proportional
A graph will show direct proportionality if the line of best fit is a straight line and passes through the origin.
59
Specular reflection
Reflection from a smooth surface. Each light ray is reflected in a single direction.
60
White dwarf
A star that has collapsed from the red giant stage to become much smaller, hotter, and denser.
61
P-wave (Primary seismic wave)
Longitudinal waves that push or pull on the material that they move through, as they move through the Earth.
62
Principle of moments
For an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that same point.
63
Diode
A non-ohmic conductor that has a much higher resistance in one direction (its reverse direction) than in the other direction (its forward direction).
64
Plugs
A plug has an insulated case and is used to connect the cable from an appliance to a socket.
65
National grid
The network of cables and transformers used to transfer electricity from power stations to consumers (I.e. homes, shops, offices, factories, etc.).
66
Physical change
A change in which no new substances are produced.
67
Ionisation
Any process which causes atoms to become charged.
68
LED (Light emitting diode)
A diode that emits light when it conducts.
69
Closed system
An object or group of objects for which the total energy is constant.
70
Resultant force
A single force that has the same effect as all the forces acting on the object.
71
Parallelogram of forms
A geometrical method used to find the resultant of two forces that do not act along the same line.
72
Rarefaction
Stretched apart.
73
Velocity
Speed in a given direction (in metres per second, m/s).
74
LDR (Light dependent resistor)
A resistor whose resistance depends on the intensity of the light it is exposed to.
75
Thermistor
A resistor whose resistance depends on the temperature of the thermistor.
76
CMBR (Cosmic Microwave Background Radiation)
Electromagnetic radiation that has been travelling through space ever since it was created shortly after the Big Bang.
77
Wavelength
The distance from one wave crest to the next (metres, m).
78
Terminal velocity
The velocity reached by an object when the drag force on it is equal and opposite to the force making it move. e.g. Air resistance and gravity.
79
Force multiplier
A lever used so that a weight or force can be moved by a smaller force.
80
Refraction
The change of direction of a light ray when it passes across a boundary between two transparent substances (including air).
81
Magnitude
The size or amount of a physical quantity.
82
Reactor core
The thick steel vessel used to contain fuel rods, control rods and the moderator in a nuclear fission reactor.
83
Neutral wire
The wire of a mains circuit that is earthed at the local substation, so its potential difference is close to zero.
84
Power
The energy transformed or transferred per second. Measured in watts, W.
85
Ion
A charged molecule or atom.
86
Seismic waves
Shock waves that travel through the Earth and across its surface as a result of an Earthquake.
87
Acceleration
The change in velocity per second (metres per second per second, m/s2). A change in speed AND/OR direction.
88
Mass
The quantity of matter in an object - a measure of the difficulty of changing the motion of an object (measured in kilograms, kg)
89
Oscilloscope
A device used to display the shape of an electrical wave.
90
Contrast medium
An X-ray absorbing substances used to fill a body organ so that the organ can be clearly seen on a radiograph.
91
Big Bang Theory
The theory that the Universe was created in a massive explosion (the Big Bang), and that the Universe has been expanding ever since.
92
Systematic errors
Cause readings to be spread, a value other than the true value, due to results differing from the true value by a consistent amount each time a measurement is made.
93
Freezing point
The temperature at which a pure substances freezes.
94
Elastic
A material is elastic if it is able to regain its shape after it has bene squashed or stretched.
95
Specific latent heat of vaporisation
The energy needed to boil away 1 kg of a substance with no change of the temperature.
96
Centripetal force
The resultant force towards the centre of a circle, acting on an object moving in a circular path.
97
Isotopes
Atoms with the same number of protons and different numbers of neutrons. This means the mass number of the isotopes will also be different.
98
Kilowatt-hour (kWh)
The electrical energy supplied to a 1 kW (1000 W) device in 1 hour.
99
Amplitude
The height of a wave crest, or depth of the trough of a transverse wave from the rest position (middle line). For oscillating motion, the amplitude is the maximum distance moved by the oscillating object from its rest position.
100
Ultrasound wave
A sound wave with a frequency greater than 20,000 Hz, above the upper limit of human hearing.
101
Optical fibre
A thin glass fibre used to transmit light signals.
102
Irradiated
When an object has been exposed to ionising radiation.
103
Vibrate
To oscillate (move to and fro) around a certain position.
104
Electromagnet
An insulated wire wrapped around an iron core that becomes magnetic when there is a current in the wire.
105
Nuclear fuel
A substance used in nuclear reactors that releases energy due to nuclear fission.
106
Gradient (of a straight-line graph)
Change of the quantity plotted on the y-axis, divided by the change in the quantity plotted on the x-axis.
107
Electromagnetic waves
Electric and magnetic disturbances that transfer energy from one place to another.
108
Ultraviolet radiation
Electromagnetic waves between visible light and X-rays on the electromagnetic spectrum.
109
Step-down transformer
An electrical device that is used to step-down (decrease) the size of an alternating potential difference.
110
Moderator
Substances in nuclear reactor that slows down neutrons from fission reactions.
111
Biofuel
Any fuel taken from living or recently living materials, such as animal waste.
112
Three-pin plug
A three-pin plug has a live pin, a neutral pin, and an earth pin. Standard use in the UK.
113
Spring constant
Force per unit extension of a spring.
114
Displacement
Distance in a given direction. Measured in metres.
115
Efficiency
Useful energy transferred by a device ÷ total energy transferred to the device.
116
Alternator
An alternating current generator.
117
Transformer
An electrical device used to change an (alternating) voltage. See also step-up and step-down transformer.
118
Gravitational field strength, g
The force exerted by gravity on an object of mass 1kg (in Newtons per kilogram, N/kg). It is also the acceleration of freefall in metres per second per second, m/s2.
119
Microwaves
Electromagnetic waves between infra-red radiation and radio waves in the electromagnetic spectrum.
120
Frequency of an alternating current
The number of complete cycles an alternating current passes through each second. The unit of frequency is Hertz, Hz.
121
Carrier waves
Waves used to carry any type of signal.
122
Normal
A straight line through a surface or boundary, perpendicular (90°) to the surface or boundary.
123
Magnetic flux density
A measure of the strength of the magnetic field, defined in terms of the force on a current-carrying conductor at right angles to the field lines.
124
Input energy
The energy supplied to a device.
125
Wasted energy
Energy that is not usefully transferred.
126
Useful energy
Energy transferred to where it is wanted in the form that is wanted.
127
Friction
The force opposing the relative motion of two solid surfaces in contact. Typically used to transform kinetic energy into thermal energy.
128
Upthrust
The upward force that acts on an object either partly or fully immersed in a fluid.
129
Conservation of energy
Conservation of energy Energy cannot be created or destroyed, only transferred to another form.
130
Virtual image
An image, seen in a lens or mirror, from which light rays appear to come after being refracted by a lens or reflected by a mirror.
131
Newton's first law of motion
If the resultant force on an object is zero, the object stays at rest if it is stationary, or it keeps moving at a constant velocity (same speed and same direction).
132
Melting point
The temperature at which a pure substances melts or freezes.
133
Nucleus
The tiny positively charged object composed of protons and neutrons, at the centre of every atom.
134
Braking distance
The distance travelled by a vehicle during the time it takes for its brakes to act.
135
Protons
Positively charged particles with an equal and opposite charge to that of an electron.
136
Diverging (concave) lens
A lens that makes parallel rays diverge (spread out).
137
Magnetic field
The space around a magnet or a current-carrying wire.
138
Real image
An image formed by a lens that can be projected on to a screen.
139
Translucent object
An object that allows light to pass through, but the light is scattered or refracted.
140
Resistance
Resistance (in ohms, Ώ) = potential difference (in volts, V) ÷ current (in amperes, A).
141
Fuse
A fuse contains a thin wire that melts and breaks the circuit if too much current passes through it.
142
Thinking distance
The distance travelled by a vehicle in the time it takes the driver to react.
143
Radioactive contamination
The unwanted presence of materials containing radioactive atoms on other materials.
144
Moment
The turning effect or force defined by the equation: moment of a force (in Newton metres, Nm) = force (in Newtons, N) x perpendicular distance from the pivot to the line of action of the force (in metres, m).
145
Free body force diagram
A diagram that shows the forces acting on an object without any other objects or forces shown.
146
Conservation of momentum
In a closed system, the total momentum before an event is equal to the total momentum after the event. Momentum is conserved in any collision or explosion, provided no external forces act on the objects that collide or explode.
147
Magnifying glass
A converging lens used to magnify a small object, which must be placed between the lens and its focal point.
148
Radio waves
Electromagnetic waves of wavelength greater than 0.10 m.
149
Newton's second law of motion
The acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object.
150
Black hole
A very dense object in space that has so much mass that almost nothing, not even light, can escape from its gravitational field.
151
X-rays
Electromagnetic waves smaller in wavelength than ultraviolet radiation, produced by X-ray tubes.
152
Radiation dose
The amount of ionising radiation a person or object receives.
153
Dynamo
A direct current generator.
154
Chain reaction
Reactions in which one reaction causes further reactions, which in turn causes further reactions, etc.
155
Opaque object
An object that light cannot pass through.
156
Density
Mass per unit volume of a substance, e.g. kg/m3
157
Echo
Reflection of sound that can be heard.
158
Half-life
The average time taken for the number of nuclei of the isotope (or mass of the isotope) to decrease by half.
159
Frequency of oscillating motion
The number of complete cycles of oscillations per second. Equal to 1 ÷ the time period. The unit of frequency is Hertz, Hz.
160
Dark matter
Matter in a galaxy that cannot be seen. Its presence is deduced because galaxies would spin much faster if their stars were only (visible) matter.
161
Main sequence
The main sequence is the life stage of a star during which it radiates energy because of fusion of hydrogen nuclei in its core.
162
Load
The weight of an object raised by a device used to lift and object, or the force applied by a device when it is used to shift an object.
163
Stopping distance
The distance travelled by the vehicle in the time it takes the driver to think and brake.
164
Static electricity
Electric charge stored on insulated objects.
165
Electromagnetic spectrum
The continuous spectrum of electromagnetic waves. (Radio, micro, infra-red, visible, ultra-violet, X-rays, gamma)
166
Carbon neutral
A biofuel from a living organism that takes in as much carbon dioxide from the atmosphere as is released when the fuel is burned.
167
Live wire
The mains wire that has a voltage which alternates between +325V and -325V in Europe.
168
Convex (converging) lens
A lens that makes parallel rays converge (meet) at a focal point.
169
Direct current (D.C.)
An electric current in a circuit that flows in a single direction only.
170
Converging (convex) lens
Converging (convex) lens A lens that makes parallel rays converge (meet) at a focal point.
171
Neutron star
The highly compressed core of a massive star that remains after a supernova explosion.
172
Line of force in an electric field
Line along which a free positive charge moves along in an electric field.
173
Transverse wave
A wave where the vibration is perpendicular to the direction of energy transfer. The wave direction is at 90° to the oscillations.
174
Fleming’s left-hand rule
A rule that gives the direction of the force on a current-carrying wire in a magnetic field according to the directions of the current and magnetic field.
175
Potential difference
A measure of the work done, or energy transferred to the lamp by each coulomb of charge that passes through it. The unit of potential difference is the volt, V.
176
Electromagnetic induction
The process of inducing a potential difference in a wire by moving the wire so that it cuts across the lines of a magnetic field.
177
Solenoid
A long coil of wire that produces a magnetic field in and around the coil when there is a current in the coil.
178
Nuclear fission reactor
Reactors that release energy steadily due to the fission of suitable radioactive isotopes, such as uranium-235.
179
Speed
The speed of an object (in metres per second, m/s) = distance moved by the object (in metres, m) ÷ time taken to move the distance travelled (in seconds, s)
180
Force
A force (in Newtons, N) can change the motion of an object.
181
Line of force
Line in a magnetic field along which a magnetic compass points – also called a magnetic field line.
182
Mechanical wave
A vibration that travels through a substance.
183
Geothermal
Energy that comes from energy released by radioactive substances deep within the Earth.
184
Tangent
A straight line drawn to touch a point on a curve so that it has the same gradient as the curve at that point.
185
Charge-Coupled Device (CCD)
An electrical device that creates an electronic signal from an optical image formed on the CCD’s array of pixels. E.g. in a digital camera
186
Specific heat capacity
The energy needed to raise the temperature of 1 kg of a substance by 1°C
187
Electrons
Tiny negatively charged particles that orbit the nucleus of an atom.
188
Vector
A vector is a physical quantity, such as displacement or velocity, that has both magnitude and direction (unlike a scalar which has magnitude only).
189
Transparent object
An object that transmits all the incident light that enters the object.
190
Diffuse reflection
Reflection from a rough surface – the light rays are scattered in different directions.
191
Mass number
The number of protons and neutrons in the nucleus of an atom. Mass = protons + neutrons
192
Wave speed
The distance travelled per second by a wave crest or trough (metres per second, m/s).
193
Pressure
The force per unit cross-sectional area for a force acting on a surface at right angles to the surface. The unit of pressure is the pascal (Pa), or Newtons per square metre (N/m2)
194
Principal focus
The point where light rays parallel to the principal axis of a lens are focussed (or, in the case of diverging lenses, appear to diverge from).
195
Black dwarf
Black dwarf A star that has faded out and gone cold.
196
Activity
The number of unstable atoms that decay per second in a radioactive substance.
197
Deceleration
Change of velocity per second when an object slows down (shown as negative acceleration).
198
Focal length
The distance from the centre of a lens to the point where light rays parallel to the principal axis are focussed (or in the case of a diverging lens, appear to diverge from).
199
Electric field
A charged object (X) creates an electric field around itself. This causes a non-contact force on any other charged object in the field.
200
Boyle’s law
For a fixed mass of gas at a constant temperature, its pressure multiplied by its volume is constant.
