Glossary Key Words Flashcards
1
Q
Acceleration
A
Change of velocity per second
2
Q
Activity
A
The number of unstable atoms that decay per second in a radioactive source
3
Q
Alpha radiation
A
Alpha particles, each composed of two protons and two neutrons, emitted by unstable nuclei.
4
Q
Alternating current
A
Electric current in a circuit that repeatedly reverses its direction.
5
Q
Alternator
A
An alternating current generator.
6
Q
Amplitude
A
The height of a wave crest or trough of a transverse wave from the rest position. For oscillating motion, the amplitude is the maximum distance moved by an oscillating object from its equilibrium position.
7
Q
Angle of incidence
A
Angle between the incident ray and the normal.
8
Q
Angle of reflection
A
Angle between the reflected ray and the normal.
9
Q
Atomic number
A
The number of protons as well as electrons in an atom. It is sometimes called the proton number.
10
Q
Beta radiation
A
Beta particles that are high-energy electrons created in, and emitted from, unstable nuclei.
11
Q
Big Bang theory
A
The theory that the universe was created in a massive explosion, and that the universe has been expanding ever since.
12
Q
Biofuel
A
Any fuel taken from living or recently living materials, such as animal waste.
13
Q
Black body radiation
A
The radiation emitted by a perfect black body (a body that absorbs all the radiation that hits it)
14
Q
Black dwarf
A
A star that has faded out and gone cold
15
Q
Black hole
A
An object in space that has so much mass that nothing, not even light can escape from its gravitational field.
16
Q
Boiling point
A
Temperature at which a pure substance boils or condenses.
17
Q
Boyle’s law
A
For a fixed mass of gas at constant temperature, its pressure multiplied by its volume is constant.
18
Q
Braking distance
A
The distance travelled by a vehicle during the time it takes for tis brakes to act.
19
Q
Carbon Neutral
A
A biofuel from a living organism that takes in as much carbon dioxide from the atmosphere as is released when the fuel is burned.
20
Q
Carrier waves
A
Waves used to carry any type of signal.
21
Q
Centripetal force
A
The resultant force towards the centre of a circle acting on an object moving in a circular path.
22
Q
Chain reaction
A
Reactions in which one reaction causes further reactions, which in turn causes further reactions etc.
23
Q
Charge - coupled device (CCD)
A
An electronic device that creates an electronic signla from an optical image formed on the CCD’s array of pixels.
24
Q
Circuit breaker
A
An electromagnetic switch that opens and cuts off current if too much current passes through it.
25
Compression
Squeezing together.
26
Concave lens
A lens that makes parallel rays diverge (spread out).
27
Condense
Turn from vapour into liquid.
28
Conservation of energy
Energy cannot be created or destroyed.
29
Conservation of momentum
In a closed system, the total momentum before an event is equal to 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.
30
Contrast medium
An X-ray absorbing substance used to fill a body organ so the organ can be seen on a radiograph.
31
Control variable
A variable that may, in addition to the independent variable, affect the outcome of the investigation, and therefore has to be kept constant or at least monitored.
32
Convection
Circulation of a liquid or gas caused by increasing its thermal energy.
33
Converging (Convex) Lens
A lens that makes light rays parallel to the principal axis converge (meet) at a point.
34
Cosmic microwave background radiation
Electromagnetic radiation that has been travelling through space ever since it was created shortly after the Big Bang.
35
Count rate
The number of counts per second detected by a Geiger counter.
36
Dark Matter
Matter in a galaxy that cannot be seen. Its presence is deducted because the galaxies would spin much faster if their stars were spin much faster if their stars were their only matter.
37
Deceleration
Change of velocity per second when an object slows down.
38
Density
Mass per unit volume of a substance.
39
Diffuse reflection
Reflection from a rough surface - the light rays are scattered in different directions.
40
Diffusion
The spreading out of particles away from each other.
41
Diode
A non-ohmic conductor that has a higher resistance in one direction (its reverse direction) than in the other direction (its forward direction).
42
Direct current
Electric current in a circuit that is in one direction only.
43
Directly proportional
A graph will show this if the line of best fit is a straight line through the origin.
44
Dispersion
The splitting of white light into the colours of the spectrum.
45
Displacement
Distance in a given direction.
46
Dissipation of energy
The energy that is not usefully transferred and stored in less useful ways.
47
Diverging (concave) lens
A lens that makes light rays parallel to the axis diverge (spread out) as if from a single point - also referred to as a concave lens.
48
Driving force
Force of a vehicle that makes it move (sometimes referred to as motive force).
49
Dynamo
A direct-current generator.
50
Earth wire
The wire in a mains cable used to connect the metal case of an appliance to earth.
51
Echo
Reflection of sound that can be heard.
52
Efficiency
Useful energy transferred by a device ÷ total energy suppled to the device.
53
Effort
The force applied to a device used to raise a weight or move an object.
54
Elastic
A material is elastic if it is able to regain its shape after it has been squashed or stretched.
55
Electric current
Flow of electric charge. The size of an electric current (in amperes, A) is the rate of flow of charge.
56
Electric field
A charged object (X) creates an electric field around itself, which causes a non-contact force on any other charged object in the field.
57
Electromagnet
An insulated wire wrapped round an iron bar that becomes magnetic when there is a current in the wire.
58
Electromagnetic induction
The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of force of a magnetic field.
59
Electromagnetic spectrum
The continuous spectrum of electromagnetic waves.
60
Electromagnetic waves
Electric and magnetic disturbances that transfer energy from one place to another.
61
Electrons
tiny negatively charged particles that move around the nucleus of an atom.
62
Endoscope
A medical instrument that uses optical fibres to see inside the body.
63
Energy levels
Specific energy values of electrons in an atom.
64
Errors
Sometimes called uncertainties.
65
Evaporate
Turn from liquid into vapour.
66
Extension
The increase in length of a spring (or a strip of material) from its original length.
67
Field lines
Line in a magnetic field along which a magnetic compass points - also called line of force.
68
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 the field.
69
Fluid
A liquid or a gas.
70
Focal length
The distance from the centre of a lens to the point where light rays parallel to the principal axis are focused (or, in the case of a diverging lens, appear to diverge from).
71
Force
A force (in newtons, N) can change the motion of an object.
72
Force diagram
A diagram showing the forces on an object.
73
Force multiplier
A lever used so that a weight or force can be moved by a smaller force.
74
Free electron
Electron that moves about freely inside a metal and is not held inside an atom.
75
Free body force diagram
A diagram that shows the forces acting on an object without any other objects or forces shown.
76
Freezing point
The temperature at which a pure substance freezes.
77
Frequency
The number of wave crests passing a fixed point every second.
78
Frequency of an alternating current
The number of complete cycles an alternating current passes through each second. The unit of frequency is the hertz (Hz)
79
Friction
The force opposing the relative motion of two solid surfaces in contact.
80
Fuse
A fuse contains a thin wire that melts and cuts the current off if too much current passes through it.
81
Gamma radiation
Electromagnetic radiation emitted from unstable nuclei in radioactive substances.
82
Generator effect
The production of a potential difference using a magnetic field.
83
Geothermal
Energy that comes from energy released by radioactive substances deep within the Earth.
84
Gradient (of a straight line graph)
Change of the quantity plotted on the y-axis divided b the change of the quantity plotted on the x-axis.
85
Gravitational field strength, g
The force of gravity on an object of mass 1 kg (in newtons per kilogram, N/Kg). It is also the acceleration of free fall.
86
Half-life
Average time taken for the number of nuclei of the isotope (or mass of the isotope) in a sample to halve.
87
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.
88
Independent variable
The variable for which values are changed or selected by the investigator.
89
Induced magnetism
Magnetisation of an unmagnetised magnetic material by placing it in a magnetic field.
90
Inertia
The tendency of an object to stay at rest or to continue in uniform motion.
91
Infrared radiation
Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum.
92
Input energy
Energy supplied to a device.
93
Internal energy
The energy of the particles of a substance due to their individual motion and positions.
94
Inverse proportionality
This is where two variables are related such that making one variable n times bigger causes the other one to become n times smaller.
95
Ion
A charged atom.
96
Ionisation
Any process in which atoms are ionised.
97
Irradiated
An object that has been exposed to ionising radiation.
98
Isotopes
Atoms with the same number of protons and different numbers of neutrons.
99
Kilowatt-hour (kWh)
The energy in electricity supplied to a 1 kW electrical device in 1 hour.
100
Latent heat
The energy transferred to or from a substance when it changes state.
101
Light-depending resistor (LDR)
A resistor whose resistance depends on the intensity of the light incident on it.
102
Light-emitting diode (LED)
A diode that emits light when it conducts.
103
Limit of proportionality
The limit for Hooke's law applied to the extension of a stretched spring.
104
Line of force
Line in a magnetic field along which a magnetic compass points - also called a magnetic field line.
105
Line of force in an electric field
Line along which a free positive charge moves along in an electric field.
106
Live wire
The mains wire that has a voltage that alternates in voltage (between +325V and 325V in Europe)
107
Load
The weight of an object raised by a device use to lift the object, or the force applied by a device when it is used to shift an object.
108
Longitudinal waves
Waves in which the vibrations are parallel to the direction of energy transfer.
109
Magnetic field
The space around a magnet or a current-carrying wire.
110
Magnetic field line
Line in a magnetic field along which a magnetic compass points - also called a line of force.
111
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.
112
Magnification.
The image height ÷ the object height
113
Magnifying glass
A converging lens used to magnify a small object which must be placed between the lens and its focal point.
114
Magnitude
The size or amount of a physical quantity.
115
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.
116
Mass
The quantity of matter in an object - a measure of the difficulty of changing the motion of an object (in Kilograms, kg)
117
Mass number
The number of proton and neutrons in a nucleus.
118
Mechanical wave
Vibration that travels through a substance.
119
Melting point
Temperature at which a pure substance melts or freezes (solidifies)
120
Microwaves
Electromagnetic waves between infrared radiation and radio waves in the electromagnetic spectrum.
121
Moderator
Substance in a nuclear reactor that slows down fission neutrons.
122
Moment
The turning effect of a 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)
123
Momentum
This equals mass (in kg) x velocity (in m/s)
124
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.
125
National Grid
The network of cables and transformers used to transfer electricity from power stations to consumers (i.e homes, shops, offices, factories, etc)
126
Neutral wire
The wire of a mains circuit that is earthed at the local substation so its potential is close to zero.
127
Neutron star
The highly compressed core of a massive star that remains after a supernova explosion.
128
Neutrons
Uncharged particles of the same mass as protons. The nucleus of an atom consists of protons and neutrons.
129
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 with the same speed in the same direction.
130
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.
131
Newton's Third Law
When two objects interact with each other, they exert equal and opposite forces on each other.
132
Normal
Straight line through a surface or boundary perpendicular to the surface or boundary.
133
Nuclear fission
The process in which certain nuclei (uranium-235 and plutonium-239) split into two fragments, releasing energy and two or three neutrons as a result.
134
Nuclear fission reactors
Reactors that release energy steadily due to the fission of a suitable isotope such as uranium-235.
135
Nuclear fuel
Substance used in nuclear reactors that releases energy due to nuclear fission
136
Nuclear fusion
The process where small nuclei are forced together to fuse and form a larger nucleus.
137
Nucleus
Tiny positively charged object composed of protons and neutrons at the centre of every tom.
138
Ohm's law
The current through a resistor at constant temperature is directly proportional to the potential difference across the reactor.
139
Opaque object
An object that light cannot pass through.
140
Optical fibre
Thin glass fibre used to transmit light signals.
141
Oscillate
Move to and fro about a certain position along a line.
142
Oscilloscope
A device used to display the shape of an electrical wave.
143
Parallel
Components connected in a circuit so that the potential difference is the same across each one.
144
Parallelogram of forces
A geometrical method used to find the resultant of two forces that do not act along the same line.
145
Perpendicular
At right angles
146
Physical change
A change in which no new substances are produced.
147
Plugs
A plug has an insulated case and is used to connect the cable from an appliance to a socket.
148
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)
149
Power
The energy transformed or transferred per second. The unit of power is the watt (W).
150
Pressure
Force per unit cross-sectional area for a force acting on a surface at right angles to the surface. TH unit of pressure is the pascal (Pa) or newton per square metre (n/m squared)
151
Primary seismic wave
Longitudinal waves that push or pull on the material that they move through as they travel through the Earth.
152
Principal focus
The point where light rays parallel to the principal axis of a lens are focused (or, in the case of a diverging lens, appear to diverge from)
153
Principle of moments
For an object in equilibrium, the su of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that point.
154
Protons
Positively charged particles with an equal and opposite charge to that of an electron.
155
Protostar
The concentration of dust clouds and gas in space that forms a star.
156
Radiation dose
Amount of ionising radiation a person receives.
157
Radio waves
Electromagnetic waves of wavelengths greater than 0.10m.
158
Radioactive contamination
The unwanted presence of materials containing radioactive atoms on other materials.
159
Rarefaction
Stretched apart.
160
Reactor core
The thick steel vessel used to contain fuel rods, control rods and the moderator in a nuclear fission reactor.
161
Real image
An image formed by a lens that can be projected on a screen.
162
Red giant
A star that has expanded and cooled, resulting in it becoming red and much larger and cooler than it was before it expanded.
163
Red supergiant
A star much more massive than the Sun will swell out after the main sequence stage to become a red supergiant before it collapses.
164
Redshift
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.
165
Reflection
The change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium.
166
Refraction
The change of direction of a light ray when it passes across a boundary between two transparent substances (including air).
167
Relay
A switch opened or closed by an iron armature that is attracted to the relay's electromagnet when a current is in the electromagnet.
168
Renewable energy
Energy from natural sources that is always being replenished so it never runs out.
169
Repeatable
A measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same results.
170
Reproducible
A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.
171
Resistance
Resistance (in ohms Ω) = potential difference (in volts, V) / current (in amperes, A)
172
Resistive forces
Forces such as friction and air resistance that oppose the motion of an object.
173
Resolution of forces
The process of considering a force in terms of two perpendicular components, which together have the same effect ona n object as the force.
174
Resultant orce
A single force that has the same effect as all the forces acting on the object.
175
Risk
The likelihood that a hazard will actually cause harm.
176
Scalar
A physical quantity, such as mass or energy, that has magnitude only (unlike a vector which has magnitude and direction).
177
Secondary seismic waves
Transverse waves that shake the Earth from side to side as they pass through.
178
Seismic waves
Shock waves that travel through the Earth and across its surface as a result of an earthquake
179
Series
Components connected in a circuit in such a way that the same current passes through them.
180
Single pendulum
A pendulum consisting of a small spherical bob suspended by a thin string from a fixed point.
181
Solenoid
A long coil of wire that produces a magnetic field in and around the coil when there isa current in the coil
182
Specific heat capacity
Energy need to raise the temperature of 1 kg of a substance by 1ºC.
183
Specific latent heat of fusion
Energy needed to melt 1 Kg of a substance with no change of temperature.
184
Specific latent heat of vaporisation
Energy needed to boil away 1 Kg of a substance with no change of temperature.
185
Specular reflection
Reflection from a smooth surface. Each light ray is reflected in a single direction.
186
Speed
The speed of an object (metres per second) = distance moved by the object (metres) / time taken to move the distance travelled (seconds)
187
Split-ring commutator
Metal contacts on the coil of a direct current motor that connects the rotating coil continuously to its electrical power supply.
188
Spring constant
Force per unit extension of a spring.
189
Static electricity
Electric charge stored on insulated objects.
190
Step-down transformer
Electrical device used to step-up the size of an alternating potential difference.
191
Stopping distance
The distance travelled by the vehicle in the time it takes for the driver to think and brake.
192
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.
193
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.
194
Tangent
A straight line drawn to touch a point on a curve so it has the same gradient as the curve at that point.
195
Terminal velocity
The velocity reached by an object when the drag force on it is equal and opposite to the force making it move.
196
Thermal conductivity
Property of a material that determines the energy transfer through ti by conduction.
197
Thermistor
A resistor whose resistance depends on the temperature of the thermistor.
198
Thinking distance
The distance travelled by the vehicle in the time it takes the driver to react
199
Three-pin plug
A three-pin plug has a live pin, a neutral pin and an earth pin.
200
Total internal reflection
The total reflection of alight ray in a transparent substance when it reaches a boundary with air or another transparent substance.
201
Transformer
Electrical device used to change an (alternating) voltage. See also Step-up transformer and Step-down transformer.
202
Translucent object
An object that allows light to pass through, but the light is scattered or refracted.
203
Tansmission
A wave passing through a substance.
