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Activity-

Number of radioactive decays per second

Alpha particle- Very ionising, but not very penetrating form of ionising radiation.

Made up of 2 neutrons (a helium nucleus)

Attract-

Pull towards

Background radiation- Radiation around us all of the time from a variety of natural and

man-made sources

Beta particle- Ionising form of radiation. It is a fast electron from the nucleus

Chain reaction- One reaction going on to create another, which creates another, and so

on, such as a nuclear fission chain reaction inside a nuclear reactor

Charge-

Property of some objects (like electrons and protons). There are two types of

charge, negative and positive

Circuit breaker- Device that detects an electrical fault and breaks the circuit

Cold fusion- Attempt to fuse hydrogen nuclei together at room temperature

Compression- Pushing together of particles caused by the passing of a sound wave

Control rods- Metal rods lowered into nuclear reactors to absorb neutrons and so

control the reaction

Current-

Movement of charged particles (usually electrons) through a material

Defibrillator- Device for providing a short flow of charge through the heart of a

patient to set it beating again

Double-insulated- Describes an appliance in which all the live components are sealed

away from the case, so the case cannot become live

Earth-

Pin/wire that carries energy safely away from an appliance if there is a fault

Electromagnetic wave- Wave that has oscillating electric and magnetic fields at right angles

to its direction of motion

Electrostatic charge- Charge from electrons that have been moved to or from an insulator

Electrostatic dust precipitator- Apparatus for removing smoke from flue gases by means of electricity

Electrostatic shock- Effect on a person who rapidly conducts charge from a charged object

Frequency-

The number of oscillations per second for a vibration

Fuse-

Thin piece of wire that melts (and breaks the circuit) if too much current

flows through it

Gamma knife- Device that focuses many separate beams of gamma rays onto a brain

tumour, giving it a much larger dose than the surrounding tissue

Gamma ray-

Very penetrating, but not very ionising form of ionising radiation. It is a

high frequency electromagnetic wave

Half-life-

Time taken for half of the nuclei in the atoms of a radioactive substance to

decay, or the time taken for the activity from a substance to half

Hydrogen bombs- Explosive device based on the fusion of hydrogen to from helium

Induce-

To produce a current by means o the dynamo effect

Insulating material- Does not allow electrons to move easily through it

Ionisation-

When electrons are either added to or removed from atoms, giving them an

overall charge

Ionising radiation- High energy particles or waves that ionise matter as they pass through

it

Live-

Pin/wire that transfers electrical energy to an appliance

Longitudinal wave- Wave whose vibrations and energy flow are in the same direction

Mass-

Amount of matter in an object. It is measured in kilograms

Medical tracer- Radioactive material emitting gamma rays that is either injected or

ingested into the body. As the rays leave the body they are detected by special

cameras producing a picture of the inside of the body

Nuclear fission- Splitting of a large nucleus when it absorbs a neutron, into two or

more smaller nuclei

Nuclear fusion- The collision of two nuclei to make one larger nucleus, often with a

large transfer of energy to heat energy

Oscillation- Back and forth motion that repeats over and over again

Radioactive dating- Process used to date materials depending on the proportional of

radioactive material they contain

Radioactive decay- Change in an atom’s nucleus that results in the emission of an

ionising radiation

Radioactive waste- By-product of nuclear reactors that contains a high concentration of

radioactive atoms

Radioisotope- Radioactive substance whose nucleus contains a specific number of

proton and neutrons

Rarefaction- Pulling apart of particles caused by the passing of a sound wave

Reflection-

Occurs when waves bounce off objects

Repel-

Push away

Resistor-

Circuit component that reduces the current flowing in a circuit

Rheostat-

Type of variable resistor

Static electricity- Build-up of charge from electrons that have been moved to or from an

insulator

Sterilisation- Use of ionising radiation (usually gamma rays) to kill microorganisms

on medical equipment

Ultrasound-

Sound waves with a very high frequency, above human hearing (20000 Hz)

Ultrasound body scan- Using ultrasound waves to produce an image of a part of the body. Most

commonly used in pre-natal scans

Variable resistors- Resistor whose resistance can be changed

Voltage-

Measure of the energy given to charge by a power supply

Wavelength-

Distance from one crest of a wave to the next crest

X-ray-

A high frequency, very penetrating electromagnetic wave

Action-

Force that acts on an objects

Aerial-

Piece of metal that absorbs radio waves to produce and alternating electrical

current

Amplitude-

The maximum displacement of a wave or oscillation (the maximum height of a wave

from the crest to the middle)

Artificial satellite- Man-made object in orbit around the earth or other planets

Atmosphere- Thin layer of gases between the solid surface of the Earth and empty

space

Centripetal force- Force acting on an object that allows it to follow a circular path. The

force must act towards the centre of the circle

Coalesce-

Join together

Coherent-

Describes different waves that have the same frequency and velocity

Constructive interference- Where overlapping waves are in step and make a wave with bigger

amplitude

Converging- Describes a lens that changes the direction of parallel rays of light

so that they meet at a focus once they have passed through the lens

Convex-

Describes a lens whose thickness decreases with increasing distance from its

centre

Critical angle- smallest angle of incidence for which TIR takes place

Destructive interference- Where overlapping waves are out of step and cancel each other out to

leave no wave at all

Diffraction- Spreading out of waves when they pass through a gap or around an

obstacle

Direction-

Where a vector quantity points to

Dispersion- The splitting of white light into its component colours (ROYGBIV)

Electromagnetic wave- Wave that has oscillating electric and magnetic fields at right angles

to its direction of motion

Focal length- Distance from the centre of a lens to the principle focus

Focus-

To aim something at one point, or the single point to which rays of light are

focusses by a lens

Geostationary orbit- An orbit where the satellite orbits at the same speed the plant rotates

Gravitational attraction- The force pulling two objects together because of their mass

Gravity-

A force that pulls one object towards another, depending on their mass and

separation

Interference- What happens when waves overlap and reinforce or cancel each other out

Inverse square law- Any relationship where if one variable increases by a factor of x

the other falls by x2. For example, if one doubles the other falls by four (2 squared)

Ionosphere- Layer of ionised particles in the upper atmosphere, on the edge of

space

Law of conservation of momentum- Law that states that momentum is conserved in collisions. Total

momentum of a system before a collision or explosion is the same as the total

momentum of the system after a collision or explosion

Magnification- How much larger the image is than the object

Medium-

Any substance that a wave passes through, e.g. air, water, metal

Microwave-

Wave that fits between radio waves and infrared in the electromagnetic spectrum

Modulation- Process of attaching information to a radio wave or other electrical

signal

Monochromatic- Describes a wave that has just one value for its wavelength.

Monochromatic light waves contain only one colour

Natural satellite- A satellite that is there because of natural causes e.g. the moon

Optical centre- point where the principle axis passes through the plane of a lens

Optimum angle- Describes the launch angle that gives a projectile maximum range

Orbit-

Path followed by a planet or satellite around a more massive object due to

gravitational attraction

Parabolic-

Describes the shape of the path followed by a projectile

Path difference- Extra distance travelled by one wave compared to another from the same

source before they overlap at the detector

Polar orbit- An orbit the goes over the north and south poles of a planet

Polarisation- Limiting the vibrations of a transverse wave to one plane only

(side-to-side, or up and down)

Polaroid filter- Sheet of plastic that only transmits light with a particular

polarisation

Principle axis- Line through the centre of a lens, at right angles to its plane

Prism-

Block of glass with triangular cross-section

Projectile- Object that travels horizontally or at an angle to the Earth’s surface

Range-

How far a projectile will travel when it is in the air

Reaction-

Force that acts against an action

Real image- Image that can be displayed on a screen

Recoil-

Backward movement induced by a force exerted on an object

Refraction- Change of speed and direction of a wave when it passes from one medium

to another

Refractive index- Sine of the angle of incidence of light divided by the sine of the

angle of refraction; a measure of the speed of light in a transparent material

Resultant-

Describes the sum of two or more quantities

Rocket-

Vehicle used to place objects in orbit, usually propelled by ejecting high

speed gas

Satellite-

An object that orbits a planet

Scalar-

Quantity where direction is not relevant

Size-

How much space something occupies

Time period- Time taken to complete one full cycle. For example, one orbit or one

full oscillation

Total Internal Reflection- When a wave travelling inside a denser medium reflects off the boundary

with another medium, and so stays inside the original material

Trajectory- Path followed by a projectile due to gravity

Transverse wave- Wave whose vibrations are at right angles to the direction of wave

motion

Vector-

Quantity that includes direction

Velocity-

How fast something is moving in a certain direction

Virtual image- Image that cannot be displayed on a screen

Visible spectrum- Range of colours present in light

Weight-

Force on an object due to the force of gravity on a planet

AND gate-

Logic gate whose output is high when both inputs are high

Base-

One of the terminals of a transistor

Battery-

Scientific name for two or more cells connected together

Bridge circuit- Full-wave rectifier made from four diodes

Capacitor-

component that stores charge, usually on a pair of parallel plates separated by

an insulator

Cell-

A device that transfers chemical energy into electrical energy

Collector-

One of the terminals of a transistor

Diode-

Component that only allows charge to flow through it in one direction

Dynamo effect- Where changes of magnetic field around conductors result in the

generation of electricity

Electric motor- Device with a rotating shaft powered by electric current interacting

with a magnet

Emitter-

One of the terminals of a transistor

Fleming’s left-hand rule- Uses thumb and first two fingers of left hand to show directions of

force, current and magnetic field in a motor

Full-wave rectification- Process of using both positive and negative parts of alternating

current to make direct current

Generator-

Machine that rotates to generate electricity

Half-wave rectification- process of allowing only the positive parts of alternating current to

pass through

Iron core-

Central part of a transformer around which the primary and secondary coils are wrapped

Isolating transformer- Transformer with the same number of turns on the primary and secondary

coils

Light-dependent resistor- Special type of resistor whose resistance decreases when the intensity

of light falling on it increases

Light-emitting diode- Diode that emits light when an electric current flows through it

Logic gate-Circuit that has two levels of input and output, low and high. The

output depends on the input(s)

Magnetic field- Region of space around a magnet where magnetic forces act on objects

Motor effect- The push on an electric current placed in a magnetic field

NAND gate-

Logic gate that is the reverse of an AND gate

Non-ohmic conductor- Conductor that produces a current-voltage graph that is not a straight

line

NOR gate-

Logic gate that is the reverse of an OR gate

NOT gate-

Logic gate with one input that reverses it

Number of turns- Number of times a wire is wrapped around in a transformer to make a

coil

OR gate-

Logic gate whose output is high when either or both inputs are high

Parallel-

Describes circuit components connected side by side route around the circuit

Positive hole- Point in a semiconductor where an electron has been freed

Potential divider- circuit that can be used to produce an output voltage that is less than

the input voltage

Power supply- source of electrical energy

Primary coil- Coil in a transformer where the input is applied

Radial field- Magnetic field whose lines of force appear to come from a single point

Rectification- Process of converting alternating current into direct current

Relay-

Switch that uses a small current flowing through an electromagnet to turn on a

greater current

Resistance- How much a component is able to slow down the flow of electrons through

it

Resistor-

Circuit component that reduces the current flowing through in a circuit

Secondary coil- Coil in a transformer from where the output is taken

Series-

Describes circuit components connected end-to-end – there is only one way

around the circuit

Slip rings- These rotate with the coil of a motor or generator, pushing against the

brushes, allowing current in and out of the coil

Split-ring emulator- Rotary switch in an electric motor that reverses current in the coil

every half revolution

Step-down transformer- Device that reduces the voltage of an electricity supply

Step-up transformer- Device that increases the voltage of an electricity supply

Switch-

Circuit component that can be used to switch the circuit on or off by creating

a gap in the circuit

Thermistor- Special type of resistor whose resistance decreases as temperature

increases

Transistor- Electronic device that can act as a switch

Truth table-

Table summarising all the possible outputs from all the different combinations

of inputs to a system of logic gates

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