AQA GCSE Combined Physics

Absorption

When a wave transfers energy to the energy stores of a material.

Acceleration

A measure of how quickly velocity is changing.

Accurate result

A result that is very close to the true answer.

Activity (radioactive)

The number of nuclei of a sample that decay per second.

Air resistance

The frictional force caused by air on a moving object.

Alpha decay

A type of radioactive decay in which an alpha particle is given out from a decaying nucleus.

Alpha particle

A positively-charged particle made up of two protons and two neutrons (a helium nucleus).

Alpha particle scattering experiment

An experiment in which alpha particles were fired at gold foil to see if they were deflected. It led to the plum pudding model being abandoned in favour of the nuclear model of the atom.

Alternating current (AC)

Current that is constantly changing direction.

Ammeter

A component used to measure the current through a component. It is always connected in series with the component.

Amplitude

The maximum displacement of a point on a wave from its rest position.

Angle of incidence

The angle the incident ray of a wave makes with the normal at a boundary.

Angle of refraction

The angle a refracted ray makes with the normal when a wave refracts at a boundary.

Anomalous result

A result that doesn't seem to fit with the rest of the data.

Atmosphere

A relatively thin layer of air that surround the Earth.

Atom

Particles that make up matter.

Atomic number

The number of protons in the nucleus of an atom.

Beta decay

A type of radioactive decay in which a beta particle is given out from a decaying nucleus.

Beta particle

A high-speed electron emitted in beta decay.

Bias

Unfairness in the way data is presented, possibly because the presenter is trying to make a particular point (sometimes without knowing they're doing it).

Bio-fuel

A renewable energy resource made from plant products or animal dung.

Braking distance

The braking distance is the distance a vehicle travels after the brakes are applied until it comes to a complete stop, as a result of the braking force.

Calibrate

Measure something with a known quantity to see if the instrument being used to measure that quantity gives the correct value.

Carbon neutral fuel

A fuel that absorbs as much CO2 from the atmosphere (when it's produced) as it releases when it's burned.

Categoric data

Data that comes in distinct categories, e.g. blood type (A+ B- etc.)

Closed system

A system where neither matter nor energy can enter or leave. The net change in total energy in a closed system is always zero.

Conduction

A method of energy transfer by heating where vibrating particles transfer energy through a material by colliding with neighbouring particles and transferring energy between their kinetic stores.

Conductor (electrical)

A material in which electrical charges can easily move.

Conservation of energy principle

Energy can be transferred usefully from one energy store to another, stored or dissipated - but it can never be created or destroyed.

Conservation of momentum

In a closed system, the total momentum before an event is the same as the total momentum after the event.

Contamination (radioactive)

The presence of unwanted radioactive atoms on or inside an object.

Continuous data

Numerical data that can have any value within a range (e.g. length).

Control experiment

An experiment that's kept under the same conditions as the rest of the investigation, but where the independent variable isn't altered.

Control group

A group that matches the one being studied, but where the independent variable isn't altered. The group is kept under the same conditions as the group in the experiment.

Control variable

A variable in an experiment that is kept the same.

Convection

A method of energy transfer by heating in liquids and gases in which energetic particles move away from hotter regions to cooler regions.

Conversion factor

A number which you must multiply or divide a unit by to convert it to another unit.

Correlation

A relationship between two variables.

Current

The flow of electric charge. The size of the current is the rate of flow of charge. Measured in amperes (A).

Decommisioning

The process of shutting down a power station so that it's completely safe and poses no risk to people or the environment.

Density

A substances mass per unit volume.

Dependent variable

The variable in an experiment that is measured.

Diode

A circuit component that only allows current to flow through it in one direction. It has a very high resistance in the other direction.

Direct current (DC)

Current that always flows in the same direction.

Discrete data

Numerical data that can only take a certain value, with no in-between vallue (e.g. number of people).

Displacement

The straight-line distance and direction from an object's starting position to its finishing position.

Distance-time graph

A graph showing how the distance travelled by an object changes over a period of time.

Drag

The frictional force caused by any fluid (a liquid or a gas) on a moving object.

Earth wire

The green and yellow wire in an electrical cable that only carries current when there's a fault. It stops exposed metal parts of an appliance from becoming live.

Efficiency

The proportion of input energy transfer which is usefully transferred. Also the proportion of input power which is usefully output.

Elastic deformation

An object undergoing elastic deformation will return to its original shape once any forces being applied to it are removed.

Elastic object

An object which can be elastically deformed.

Elastic potential energy store

Anything that has been stretched or compressed, e.g. a spring has energy in its elastic potential energy store.

Electromagnet

A solenoid with an iron core.

Electromagnetic (EM) spectrum

A continuous spectrum of all the possible wavelengths of electromagnetic waves.

Electron

A subatomic particle with a relative charge of -1 and a relative mass of 1/2000.

Energy store

A means by which an object stores energy. There are different types of energy store.

Equilibrium

A state in which all the forces acting on an object are balanced, so the resultant force is zero.

Fair test

A controlled experiment where the only thing being changed is the independent variable.

Fleming's left hand rule

The rule used to work out the direction of the force produced by the motor effect. The first finger points in the direction of the magnetic field, your second finger points in the direction of the current and your thumb points in the direction of the force.

Fluid

A substance that can flow either a liquid or a gas.

Force

A push or a pull on an object caused by it interacting with something.

Fossil fuel

the fossil fuels are coal, oil and natural gas, they are non-renewable energy resources that we burn to generate electricity.

Free body diagram

a diagram that shows all the forces acting on an isolated object, the direction in which the forces are acting and there magnitude.

Frequency

the number of complete waves passing a certain point per second or the number of waves produced by a source per second, measured in Hertz, Hz

Frequency density

the height of a bar on a histogram, it is found by the frequency divided class width

Friction

a force that opposes an objects motion, it acts in the opposite direction to the motion.

Gamma decay

A type of radioactive decay in which a gamma ray is given out from a decaying nucleus.

Gamma ray

A high-frequency, short-wavelength electromagnetic wave.

Geiger-Müller

A particle detector that is used with a counter to measure count rate.

Geothermal power

A renewable energy resource where energy is transferred from the thermal energy stores of hot rocks underground and is used to generate electricity or to heat buildings.

Gradient

The slope of a line graph. It shows how quickly the variable on the y-axis changes with the variable on the x-axis.

Gravitational potential energy store

Anything that has mass and is in a gravitational field has energy in its gravitational potential energy store.

Greenhouse effect

The process by which gases in the Earth's atmosphere block radiation from the Sun from leaving the atmosphere. This causes the overall temperature of the atmosphere to rise.

Half-life (nuclei)

The time it takes for the number of nuclei of a radioactive isotope in a sample to halve.

Half-life (activity)

The time it takes for the count rate (or activity) of a radioactive sample to fall to half its initial level.

Hazard

Something that has the potential to cause harm.

Hydroelectric power station

A power station in which a dam is built across a valley or river which holds back water, forming a reservoir. It allows water to flow out of the reservoir through turbines at a controlled rate. This turns the turbines, which are attached to generators and can generate electricity.

Hypothesis

A possible explanation for a scientific observation.

Independent variable

The variable in an experiment that is changed.

Induced magnet

A magnetic material that only has its own magnetic field, and behaves as a magnet, while it is inside another magnetic field.

Inelastic deformation

An object undergoing inelastic deformation will not return to its original shape once the forces being applied to it are removed.

Inertia

The tendency of an object to remain stationary or continue travelling at a constant velocity.

Inertial mass

The ratio between the resultant force acting on an accelerating object and its acceleration.

Infrared (IR) radiation

A type of electromagnetic wave that is given out by all objects. it can also be absorbed by objects which makes the object hotter.

Internal energy

The total energy that a system's particles have in their kinetic and potential energy stores.

Ion

An atom in which the number of electrons is different to the number of protons, giving it an overall charge.

Ionising radiation

Radiation that has enough energy to knock electrons off atoms.

Irradiation

Exposure to radiation.

Isotope

A different form of the same element, which has atoms with the same number of protons (atomic number), but a different number of neutrons (and so different mass number).

Kinetic energy store

Anything that's moving has energy in its kinetic energy store.

Latent heat

The energy required to change the state of a substance without changing its temperature.

Light-dependent resistor

A resistor whose resistance is dependent on light intensity. The resistance decreases as light intensity increases.

Limit of proportionality

The point beyond which the force applied to an elastic object is no longer directly proportional to the extension of the object.

Line of action (of a force)

A straight line passing through the point at which the force is acting in the same direction as the force.

Linear graph

A straight line graph for which y=mx+c, where m=gradient and c=y-intercept.

Live wire

The brown wire in an electrical cable that carries an alternating potential difference from the mains.

Longitudinal waves

A wave in which the oscillations are along the same line as the direction of energy transfer.

Lubricant

A substance (usually a liquid) that can flow easily between two objects. Used to reduce friction between surfaces.

Magnetic field

A region where magnetic materials (like iron and steel) and current-carrying wires experience a force.