• PHYSICS KEYWORDS AQA gcse

PHYSICS KEYWORDS

Acceleration The rate of change of velocity, acceleration depends on the mass of the object and the force applied.

Alpha A radioactive emission with low penetrating power, which can be blocked by paper.

Alternating Current (A.C.) An electric current that constantly changes direction.

Ammeter A device which measures current in series and parallel circuits, measured in amperes (A).

Ampere (A) The unit of electric current.

Amplitude The maximum displacement from the mean position in a transverse wave. In sound it is the measure of the loudness of the sound.

Attraction A force, which occurs between two charged objects if they have dissimilar charges, for example 'positive and negative' (coming together force)

Background Some radioactivity occurs naturally from for example space or rocks and is described as 'background' radioactivity.

Balanced In electricity when there is an equal number of positive and negative charges present on an object.

Balanced When two things for example forces are equal, so they cancel each other out.

Beta A radioactive emission with moderate penetrating power can be blocked by thin sheets of aluminium.

Big Bang The accepted theory of how the Universe began, which states that all matter was created in an explosion from a single point in space at a single time, the matter was thrown outwards and has continued to travel outwards ever since.

Biofuel Energy sources derived from recently living organic matter for example biodiesel is made from vegetable oils and animal fats and can be used in some cars. Bioethanol is produced from the fermentation of some crops for example corn or sugarcane.

Cancer A malfunction of the human body where growths of undifferentiated tissue occurs which can be malignant and fatal, often linked with radioactivity.

Charges These are either positive or negative; they exert forces on one another. If an object is 'charged' then it has a set of charges.

Chemical Form of energy, things which release energy as a result of a chemical reaction, for example burning of a fuel, respiration of food in the body, or the chemicals in a battery.

CMBR Cosmic microwave background radiation present in the universe and left over from the big bang, used as evidence to support the big bang.

Components A part of an electrical circuit, for example the bulbs or switch or diode.

Compression A place on a longitudinal wave where the density is the maximum. For example, in sound waves where the air is the least spread out.

Compression Solid objects can be compressed (squashed) if forces are applied to them.

Condensation When a vapour turns to a liquid on cooling, heat is given out during this change.

Conduction When heat energy is moved because the vibrating particles in a solid conductor pass it on, metals are the best conductors.

Conservation Describes the importance of saving or restricting the use of an important resource, such as the non-renewable energy sources.

Convection When heat energy is moved because of the movement of more energetic particles in liquids and gases.

Current Electric current is the flow of electrons or ions.

Data logger Electrical computer equipment used to measure and record information such as temperature, sound levels, pH and oxygen levels.

Diffracted This word describes the circular bending of waves when they pass through a small gap.

Diode A component, which lets electric current pass through in only one direction.

Direct current (D.C.) An electric current that always flows in the same direction.

Dissipated This word describes how heat energy becomes spread out into the environment.

Doppler effect This phenomenon is the observed change in wavelength and frequency of waves produced from a moving object. The Doppler effect is observed when an ambulance passes and overtakes you.

Dynamo The dynamo principle is the production of a voltage and or current in a coil when there is movement between it and a magnetic field.

Echoes These are reflections of sound waves.

Efficiency When energy is transferred only part of it may be usefully transferred, the rest is ‘wasted’. Efficiency is used to illustrate the amount of usefully transferred energy. To calculate the efficiency of a device use either equation below:

Efficiency = useful energy out/total energy in (x100%) Efficiency = useful power out/total power in (x100%)

Elastic (strain) Form of energy possessed by a stretched spring or elastic band, when the spring is released this energy is released and will do work.

Elastic-limit The point at which a spring or wire will no longer return to its original shape.

Electrical Energy possessed by electrical charge as it moves around a circuit.

Electrical Power This is the amount of electrical energy an appliance transfers. It depends on how long the appliance is switched on and its power rating. P is power and is measure in units called kilowatts, kW.

Electromagnet Found in electric bells, and relays, the electricity moving through the coil of wire makes it magnetic.

Electromagnetic Spectrum (EMS) An important and diverse family of waves, which include radio waves as well as gamma waves, they have many important uses including communication and medical.

Electrostatics This is the transfer of electrons to or from insulators, caused by negative or positive charge, electrostatic friction causes common electrostatic phenomena.

Emission Something, which is given out.

Energy An object has energy if it is able to do something or make something happen, unit is joules (J).

Evaporation The loss of the most energetic particles from the surface of a liquid, it depends on the surface area of the water, temperature, and humidity and movement of the surrounding air.

Extension Solid objects like metal wires and springs can be extended (made longer) if forces are applied to them.

Field A magnetic field is the space in which a permanent magnet or conductor carrying an electric current experiences a force.

Force Something, which can cause (1) movement, (2) change in direction (3) change in shape.

Fossil fuel Chemical energy sources derived from the remains of ancient biomass, wood turns into coal, and plankton turns into natural gas and crude oil. The fuels are burnt to heat water or air.

Frequency The number of waves per second measured in a unit called hertz (HZ). One hertz means one wave in one second. The symbol is ‘f’.

Friction A type of force, which particularly effects motion, for example air resistance on a falling parachute.

Fuse Device used in plugs of electrical appliances to protect them from too much electricity.

Galaxy A vast number of star systems held by gravitational forces.

Gamma radiation A radioactive emission with high penetrating power which can be blocked by concrete or lead, it is also a part of the electromagnetic spectrum.

Gamma wave Member of the EMS, which comes at the end of the spectrum, they have the shortest wavelength and the highest frequency they carry the most energy and are the most harmful waves. They are used in hospital scanning equipment. Over exposure cause cancer, and hospitals use the same waves to target and destroy cancers.

Geiger-Muller (GM) A tube and counter, which is used to detect and measure radioactivity.

Generator An important piece of equipment found in power stations. It consists of a magnet inside coils of wire, when made to spin it generates an electrical voltage.

Geothermal An energy source which uses the heat energy from hot rocks which are close to the surface of the Earth. The energy can be utilized to heat water and generate electricity.

Gravitational energy Energy that an object possesses because it is raised above the ground, for example the gravitational energy of the raised water in a hydro-electric dam.

Gravitational-potential energy The energy an object possesses because of its position.

Gravity The force of attraction between two objects. The moon is kept in orbit around earth because of the gravitational attraction between earth and the moon.

Heat exchanger This is any equipment which is used to transfer heat from one place or material or another material. Heat exchangers are used widely for example in cars, fridges and air conditioning units.

Hertz (Hz) The unit of frequency.

Hydraulic-systems Systems that use pressure in a liquid to send forces to where they are needed.

Hydroelectric An energy source which uses the gravitational potential energy held in water, which has been raised by a dam, the falling water rotates the turbine, which is coupled to an electrical generator so a voltage is produced.

Immersion heater A piece of laboratory heating equipment, which is used to heat up blocks of metal or beakers of water.

Incidence ‘Original’ for example original ray of light.

Induction To induce or to make something happen, for example electric current will induce a magnetic field around the wire that is carrying it.

Infrared Electromagnetic waves which are given off by hot bodies or objects. A member of the EMS, which come after microwaves and before visible light waves, used in heating devices, and remote controls for televisions, DVD players etc.

Insulation Material, which can reduce heat loss, for example fibreglass in loft insulation.

Insulation Material for example plastic, which doesn't conduct electricity. (Like the plastic sheathing in cables).

Isotopes This is where an element like carbon, has two types of atom, each with different numbers of neutrons in the nucleus.

Joules This is the unit of energy (J).

Kilowatt Power is measure in this unit; 1000 watts are equal to 1 kW.

Kilowatt-hour (kWh) The unit of electrical energy transferred by an electrical appliance.

Kinetic energy Form of energy possessed by objects, which are in motion.

Laterally inverted This word is used to describe an image, which has been horizontally transposed, like the image in a mirror, where left becomes right.

Lesley’s cube A piece of laboratory equipment shaped like a cube and filled with water, which is used to demonstrate the different abilities of different types of surfaces to emit or reflect infrared radiation.

Light energy Form of energy, which is radiated, and produced by luminous objects, for example the sun or a bulb.

Light-year The distance travelled by light in one earth year, used as a unit of distance.

Longitudinal A type of wave where particles move from side to side for example sound. This movement is parallel to the direction in which the energy moves.

Loudspeaker A device, which turns electrical current into sound.

Luminous Gives out its own light for example stars.

Magnetic A type of force exhibited by a few metals for example iron, cobalt, nickel.

Mass This means the amount of material a body or object possess, measure in a unit called kilogram (kg).

Mechanical wave Such as the water waves and earthquakes can be longitudinal or transverse.

Microphone Device, which changes sound waves into varying electric current.

Microwaves Member of the EMS, which comes after radio waves and before infrared, wavelength ranges from 1mm to 1m. Used in cooking because they excite and heat water molecules.

Milky Way The galaxy in which our solar system resides

Moment The name moment is given to the turning effect of a force, the size of the moment depends on the size of the force multiplied by the distance from the pivot.

Moon A non-luminous space body, which orbits planets.

National grid The collective name given to the power stations, transformers, pylons and cables which distribute electricity around the country.

Newton (N) The unit of force.

Non-luminous Does not give out its own light, for example moon and planets, can only be seed if they reflect the light from stars like the sun.

Non-renewable Energy sources which are finite, for example coal, oil, gas.

Normal In ray diagrams the normal is an imaginary line drawn as a dashed line and at right angles to the mirror in reflection experiments or block in refraction experiments.

Nuclear fission A reaction of the nucleus where a large unstable nucleus splits apart forming a smaller more stable nucleus. Particles or energy are emitted from the nucleus as well as heat during the process.

Nuclear Form of energy, things that release energy as a result of changes in the nuclei of their atoms, (radioactive materials).

Ohm ( Ω ) The unit of resistance.

Orbit Describes how a space body moves around other space bodies.

Oscilloscope (CRO) A device which displays patterns of sound waves.

Parallel An electrical circuit in which the components are laid side by side, in 'parallel'.

Pascal (Pa) The unit of pressure.

Pattern Describes how the field lines fall.

Payback time This phrase is used to describe how long it takes a customer to pay for an appliance with any savings that have been made by using the equipment.

Penetrating Describes how far radioactive emissions can travel before being blocked.

Perpendicular At right angles.

Pitch This word describes a property of sound waves, a pitch can be 'high' when the frequency or the tone of a note is high, or 'low' when frequency or tone is low.

Pivot A point about which an object can turn for example the pivot on a seesaw.

Plain mirror A common mirror has a flat reflective surface, and produces an virtual, upright image, which is laterally inverted.

Planets A non-luminous space body, which orbits stars.

Plutonium A man-made radioactive silvery, metal produced when uranium breaks down, first discovered in 1940. It is also used as a nuclear fuel.

Potential difference The amount of energy (work done) per unit charge (coulomb) needed to move a charged particle between two points in an electric circuit; voltage.

Power1 Electrical power is the rate of transfer of electrical energy (J/S).

Power2 The rate of doing work, power (W) = work done (J) divided by time taken (s).

Precipitator A device used in the chimneys of power stations, which uses electrostatics to reduce pollution.

Pressure The force acting on a unit area of surface.

Prism A triangular/pyramid block of glass, which can be used to split up the different wavelengths of white light to show the complete spectrum.

Radiation Radiation is one way in which heat is moved. Hot objects emit infrared radiation into the cooler environment; conversely a cold body absorbs infrared radiation from a hotter environment.

Radio waves Member of the EMS with the longest wavelength carries the least energy and is the least harmful, used in communication.

Radioactivity The spontaneous emission of energy from unstable nuclei, a random process unaffected by physical or chemical factors.

Rarefaction A place on a longitudinal wave where the density is the least. For example, in sound waves where the air is the most spread out.

Red shift This is evidence to support the big bang theory. When we view the light from distant stars it contains more wavelengths from the red end of the spectrum, the furthest and fastest stars have show the biggest red shift.

Reflection A property of waves including light and sound, the reflection of light is the change in direction of the light when it strikes a surface or mirror.

Refraction A property of waves, including light and sound, the refraction of light is the change in direction of the light when it passes from one medium to another.

Renewable Energy resources, which are not finite, for example solar, tidal, hydroelectric, wave, wind.

Repulsion A force, which occurs between two charged objects if they have similar charges for example 'positive and positive’ (pushing away force).

Resistance The change in current in an electrical circuit as a result of change in resistance and/or voltage within the circuits. (This is the slowing down or stopping of the electricity in a circuit by material).

Resistor The name given to a material or component that has resistance, it resists the flow of electricity, for example a bulb.


Rotation To turn around on its own axis, this is what earth does and in it causes day and night, and apparent movement of the stars.

Sankey diagram A diagram, which is used to illustrate the energy transfers within a system or appliance.

Satellites Objects that move in orbit around the earth or another planet, the moon is a satellite of the earth, there are also artificial satellites, which have been put into orbit by man.

Series An electric circuit, which has the components following on one after another.

Sheathing Plastic which coats the metal wire in cables.

Solar cells Solar cells are designed to absorb solar radiation and convert it into electricity.

Solar panels Solar panels contain water that is heated by radiation from the Sun. This water may then be used to heat buildings or provide domestic hot water.

Sound Form of energy, air compressions from a source like a loudspeaker.

Specific Heat Capacity This means the amount of heat required to raise the temperature of 1kg of a substance by one degree Celsius, the specific heat capacity of water is 4200 J/kgC

Speed The distance travelled by an object in a certain amount of time, speed (m\s) = distance (m) divided by time taken (s). (A measure of how fast something is travelling).

Spontaneous Describes how a radioactive atom breaks down of its own accord - without being influenced.

Star Luminous space body, which are really gaseous, masses generating heat and light.

Sterilisation Processes of removing all germs.

Sun The name given to the star in our star system, a source of light and other electromagnetic radiations. It is at the centre of our solar system.

Surface area This is a measure of the amount of physical surface a chemical possesses, powder has a greater surface area than a big lump.

Switch A part of an electrical circuit, which can be open or closed to turn the circuit on or off.

Temperature probe An electrical thermometer attached to a data logger, used by scientists to make accurate and continuous temperature measurements.

Terminal velocity The constant velocity, which is reached by falling objects travelling in air and other fluids.

Thermal Also called heat energy, all things because of the motion of their molecules have this, the higher the temperature the faster the motion, the greater the energy.

Tilt The earth tilts on its axis relative to its plane of orbit, this tilting is responsible for seasonal changes and changes in the length of day light time.

Transformer These are devices, which are used to increase (step up) or reduce (step down) the voltage of an A.C. supply, which is fed into them, it makes the transmission more efficient.

Transmission Describes how electricity is taken from the power station to for example a house.

Transverse A type of wave where particles move up and down for example water. This movement is at right angles to the direction in which the energy moves.

Turbine An important piece of equipment found in power stations. Various methods are used to make it spin or turn, since it is connected (or coupled) to an electrical generator this is also made to spin thereby creating electricity.

Ultrasound Sound waves which cannot be heard by humans, used in medicine, and submarines and by bats.

Ultraviolet Member of the EMS, which come after infrared waves and before x-rays. They are used in tanning, overexposure can be harmful.

Unbalanced When two things for example forces are not equal so an object may change shape or direction or may move. When one type of charge is greater than the other, for example more 'positive' than 'negative'.

Universe Made up of innumerable galaxies.

Upright This word is used to describe an image, which is orientated the same way up as the object.

Uranium A radioactive silvery metal element discovered in 1789, and named after the planet Uranus. It used as a fuel in nuclear power stations because it undergoes a chain reaction of nuclear fission, which releases vast amounts of heat energy.

U-value U-values measure how effective a material is as an insulator. The lower the U-value, the better the material is as an insulator.

Vacuum A place where there is no matter.

Variable Describes how something changes.

Velocity The speed of an object in a particular direction.

Virtual image An image, which ‘appears’ to be in a particular place but is not really there, so it is imaginary.

Visible Member of the EMS, which come after infrared waves and before ultraviolet. They are detected by human eyes because of sensitive receptor cells on the retina.

Volt (V) The unit of voltage.

Voltage An electricity term, which describes the amount of energy, carried by the current.

Voltmeter A device used to measure voltage in series and parallel circuits.

Volume This is a measure of the amount of physical space an object possesses, & is measure in units of m3 or cm3.

Watt (W) The unit of power.

Wave A phenomenon, which transfers energy but not matter.

Wave equation All waves obey the wave equation: v = f x l. Where v is speed in metres per second, m/s; f is frequency in hertz, Hz and l is wavelength in metres, m

Wavelength The distance (m) between consecutive crests or troughs in a transverse wave. Measure in metre units. The symbol is 

Weight A type of force so measured in newtons, it is the gravitational force of attraction between the object and earth.

Work The transfer of energy as a result of work done, ( work (J) = force (N) multiplied by distance (m)).

X-rays Member of the EMS, which come after ultraviolet and before gamma waves. They are used in hospital scanning equipment, over exposure can be harmful.

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