Speed: The distance travelled by an object per unit time.
Velocity: The speed of an object in a stated direction.
Acceleration: The rate of change of an object's velocity.
Force: The action of one body on a second body that causes its velocity or shape to change.
Newton: The force required to give a mass of 1kg an acceleration of 1 m/s2.
Scalar quantity: A quantity that does not have a directional component (e.g. speed).
Vector quantity: A quantity that has a directional component (e.g. velocity).
Mass: The amount of matter in a substance (measured in kilograms, kg).
Weight: The force of gravity acting on an object (measured in newtons, N).
Density: A measure of how much mass is contained in a given unit volume (density = mass/volume, usually measured in g/cm3, or kg/m3) .
Renewable: A resource that can be created again in a human time scale (e.g. wood biomass), or one that will never run out (e.g. solar energy).
Non-renewable: A resource that will one day run out (e.g. coal, uranium).
Fusion: The joining of atomic nuclei to form a larger nucleus. Fusion is how energy is released from stars like our sun.
Fission: The splitting of an unstable nucleus to produce smaller nuclei. The release of energy from these reactions is harnessed in nuclear power stations.
Evaporation: A change of state from liquid to gas below the boiling point of that liquid. Evaporation occurs at the surface of the liquid.
Boiling: A change of state from a liquid to a gas. This occurs only at the boiling point of that liquid. Boiling occurs throughout the volume of the liquid.
Freezing: A change of state from a liquid to a solid.
Condensing: A change of state from a gas to a liquid.
Melting: A change of state from a solid to a liquid.
Thermal capacity: The amount of heat required to change a substance's temperature by a given amount.
Specific heat capacity (SHC): The specific heat capacity of a substance is the heat energy required to raise 1kg of the substance by 1 degree Celsius (measured in J/kg°C).
Latent heat: The heat released or absorbed by a body as it changes state without a change in temperature.
Specific latent heat of a substance: Is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.
Latent heat of vaporisation: The heat released by a body as it changes from a gas to a liquid, or absorbed by a body as it changes from a liquid to a gas.
Latent heat of fusion: The heat released by a body as it changes from a liquid to a solid, or absorbed by a body as it changes from a solid to a liquid.
Conduction: The flow of heat through matter from places of higher temperature to places of lower temperature without movement of the matter as a whole.
Convection: The transfer of heat energy through a fluid (gas or liquid) from places of higher temperature to places of lower temperature by movement of the fluid itself.
Radiation: The transfer of heat energy by electromagnetic radiation (infra-red radiation in particular). It does not require a medium.
Frequency: The number of wavelengths per second (1 hertz = 1 wavelength per second).
Wavelength: The distance from one point on a wave to the same point on the next wave.
Amplitude: The maximum displacement of a wave from its equilibrium position.
Longitudinal: The oscillations of the wave are parallel to the motion of the wave (e.g. sound waves).
Transverse: The oscillations of the wave are perpendicular to the motion of the wave (e.g. light waves).
Refraction: The speeding up or slowing down of a wave as it passes from one medium to another. This is often accompanied by a change in direction as well.
Critical angle: The angle of incidence at which maximum refraction occurs. Any angle larger than this will result in total internal reflection.
Total internal reflection (TIR): For waves travelling from a more dense medium to a less dense one, any angle larger than the critical angle will result in all of waves being reflected back into the medium.
Principal focus: Also called the focal point, it is the point on the axis of a lens or mirror to which parallel rays of light converge, or from which they appear to diverge after refraction or reflection.
Focal length: The distance from the centre of a lens, or the reflecting surface of a mirror, to the principal focus.
Audible range: The range of frequencies that an animal can detect, from the lowest pitch to the highest pitch. For humans this is 20Hz to 20,000Hz.
Permanent magnet: A material that is hard to magnetise but retains its magnetic properties once magnetised. Made from hard magnetic materials like steel.
Temporary magnet: A material that gains and loses its magnetic properties easily. These form the basis of electromagnets as they quickly demagnetise once the current is switched off. Made from soft magnetic materials like iron.
Current: A flow of electricity through a conductor, measured in amps, A.
Potential difference (p.d.): The difference, measured in volts, in electric potential between two points.
Electromotive force (emf): Refers to the voltage generated by a battery, measured in volts.
Transformer: A device that transfers an alternating current from one circuit to another circuit, usually with an increase (step-up transformer) or decrease (step-down transformer) of voltage.
Generator: A device for converting mechanical energy into electrical energy by electromagnetic induction.
Motor: A device that converts electrical energy into mechanical energy.
Alternating current (ac): An electric current that reverses direction in a circuit at regular intervals.
Direct current (dc): An electric current that flows in one direction only.
Electro-magnetic induction
When a wire is moved in relation to a magnetic field a current is induced in the wire.
Radioactive decay: Occurs when an unstable nucleus emits ionising radiation and decays into another nuclide.
Half life: The time taken for half of a radioactive material to decay into another substance.
Ionising radiation: Radiation that has enough energy to strip electrons off atoms (thus creating ions).
Electricity: A flow of charge/electrons.
Velocity: The speed of an object in a stated direction.
Acceleration: The rate of change of an object's velocity.
Force: The action of one body on a second body that causes its velocity or shape to change.
Newton: The force required to give a mass of 1kg an acceleration of 1 m/s2.
Scalar quantity: A quantity that does not have a directional component (e.g. speed).
Vector quantity: A quantity that has a directional component (e.g. velocity).
Mass: The amount of matter in a substance (measured in kilograms, kg).
Weight: The force of gravity acting on an object (measured in newtons, N).
Density: A measure of how much mass is contained in a given unit volume (density = mass/volume, usually measured in g/cm3, or kg/m3) .
Renewable: A resource that can be created again in a human time scale (e.g. wood biomass), or one that will never run out (e.g. solar energy).
Non-renewable: A resource that will one day run out (e.g. coal, uranium).
Fusion: The joining of atomic nuclei to form a larger nucleus. Fusion is how energy is released from stars like our sun.
Fission: The splitting of an unstable nucleus to produce smaller nuclei. The release of energy from these reactions is harnessed in nuclear power stations.
Evaporation: A change of state from liquid to gas below the boiling point of that liquid. Evaporation occurs at the surface of the liquid.
Boiling: A change of state from a liquid to a gas. This occurs only at the boiling point of that liquid. Boiling occurs throughout the volume of the liquid.
Freezing: A change of state from a liquid to a solid.
Condensing: A change of state from a gas to a liquid.
Melting: A change of state from a solid to a liquid.
Thermal capacity: The amount of heat required to change a substance's temperature by a given amount.
Specific heat capacity (SHC): The specific heat capacity of a substance is the heat energy required to raise 1kg of the substance by 1 degree Celsius (measured in J/kg°C).
Latent heat: The heat released or absorbed by a body as it changes state without a change in temperature.
Specific latent heat of a substance: Is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.
Latent heat of vaporisation: The heat released by a body as it changes from a gas to a liquid, or absorbed by a body as it changes from a liquid to a gas.
Latent heat of fusion: The heat released by a body as it changes from a liquid to a solid, or absorbed by a body as it changes from a solid to a liquid.
Conduction: The flow of heat through matter from places of higher temperature to places of lower temperature without movement of the matter as a whole.
Convection: The transfer of heat energy through a fluid (gas or liquid) from places of higher temperature to places of lower temperature by movement of the fluid itself.
Radiation: The transfer of heat energy by electromagnetic radiation (infra-red radiation in particular). It does not require a medium.
Frequency: The number of wavelengths per second (1 hertz = 1 wavelength per second).
Wavelength: The distance from one point on a wave to the same point on the next wave.
Amplitude: The maximum displacement of a wave from its equilibrium position.
Longitudinal: The oscillations of the wave are parallel to the motion of the wave (e.g. sound waves).
Transverse: The oscillations of the wave are perpendicular to the motion of the wave (e.g. light waves).
Refraction: The speeding up or slowing down of a wave as it passes from one medium to another. This is often accompanied by a change in direction as well.
Critical angle: The angle of incidence at which maximum refraction occurs. Any angle larger than this will result in total internal reflection.
Total internal reflection (TIR): For waves travelling from a more dense medium to a less dense one, any angle larger than the critical angle will result in all of waves being reflected back into the medium.
Principal focus: Also called the focal point, it is the point on the axis of a lens or mirror to which parallel rays of light converge, or from which they appear to diverge after refraction or reflection.
Focal length: The distance from the centre of a lens, or the reflecting surface of a mirror, to the principal focus.
Audible range: The range of frequencies that an animal can detect, from the lowest pitch to the highest pitch. For humans this is 20Hz to 20,000Hz.
Permanent magnet: A material that is hard to magnetise but retains its magnetic properties once magnetised. Made from hard magnetic materials like steel.
Temporary magnet: A material that gains and loses its magnetic properties easily. These form the basis of electromagnets as they quickly demagnetise once the current is switched off. Made from soft magnetic materials like iron.
Current: A flow of electricity through a conductor, measured in amps, A.
Potential difference (p.d.): The difference, measured in volts, in electric potential between two points.
Electromotive force (emf): Refers to the voltage generated by a battery, measured in volts.
Transformer: A device that transfers an alternating current from one circuit to another circuit, usually with an increase (step-up transformer) or decrease (step-down transformer) of voltage.
Generator: A device for converting mechanical energy into electrical energy by electromagnetic induction.
Motor: A device that converts electrical energy into mechanical energy.
Alternating current (ac): An electric current that reverses direction in a circuit at regular intervals.
Direct current (dc): An electric current that flows in one direction only.
Electro-magnetic induction
When a wire is moved in relation to a magnetic field a current is induced in the wire.
Radioactive decay: Occurs when an unstable nucleus emits ionising radiation and decays into another nuclide.
Half life: The time taken for half of a radioactive material to decay into another substance.
Ionising radiation: Radiation that has enough energy to strip electrons off atoms (thus creating ions).
Electricity: A flow of charge/electrons.
