Paper 2 Definitions Flashcards
Electric potential?
Work done in bringing a positive charge from infinity to a distance r away from a charge Q.
Electric potential difference?
Difference in electrical potential between two points in an electric field.
Coulombs law?
Force between two charges is proportional to the product of the charges.
Electric field strength?
Force per unit charge acting on a small positive test charge at that point.
Capacitance?
Charge required to cause unit potential difference in a conductor.
Permittivity?
A measure of how difficult it is to generate an electric field in a medium.
Dielectric?
A material whose molecules polarise inside an electric field.
Magnetic flux density?
Force on one metre of wire carrying a current of 1 amp at right angles to the magnetic field.
Magnetic flux density?
Strength of the magnetic field or the number of field lines per unit area.
Induced emf?
Rate of change of flux linkage.
Faraday’s law?
Induced emf is directly proportional to the rate of change of flux linkage.
Lenz’s law?
The induced emf is always in such a direction as to oppose the change that caused it.
AC?
One that changes direction with time.
Transformers?
Devices that make use of electromagnetic induction to change the size of the voltage for alternating current.
Eddy currents?
Looping current induced by the changing magnetic flux, resulting in the reduction of the value of the induced emf in the secondary coil.
Field?
A region where a body will experience a non-contact force.
Gravitational fields?
A region of space which any mass will experience a force of attraction.
Gravitational field strength?
Force per unit mass on a small test mass placed in the field.
Gravitational potential?
The GPE that a unit mass at that point would have.
Equipotentials?
Lines which connect points of the same gravitational potential.
Escape velocity?
Minimum velocity required for an object to escape from the planet when fired vertically from the surface.
Synchronous orbit?
When an orbiting object has an orbital period equal to the rotational period of the object it is orbiting.
Internal energy of a body?
Sum of the randomly distributed kinetic and potential energies of all its particles.
Specific heat capacity of a substance?
Amount of energy needed to raise the temperature of 1kg of the substance by 1K.
Latent heat?
Energy needed to break the bonds that hold the particles in place.
Specific latent heat of fusion or vaporisation?
Quantity of thermal energy needed to be gained or lost to change the state of 1kg of a substance.
Boyle’s law?
At a constant temperature the pressure p and volume V of a gas are inversely proportional.
Charle’s law?
At constant pressure, the volume V of a gas is directly proportional to its absolute temperature, T.
Pressure law?
At constant volume, the pressure p of an ideal gas is directly proportional to its absolute temperature T.
Molecular mass?
Sum of all the masses of all the atoms that make up a single molecule.
Avogadro’s constant?
Number of atoms in 12g of carbon 12.
Molar mass?
Mass that 1 mole of a substance would have.
Alpha?
2p, 2n, helium nucleus.
Beta minus?
Fast moving electron.
Beta plus?
Fast moving positron.
Gamma?
High energy, high frequency, short wavelength wave.
Intensity of radiation?
Amount of radiation per unit area.
Activity?
Number of nuclei that decay each second.
Decay constant?
Probability of a specific nucleus decaying per unit time, and is a measure of how quickly an isotope will decay.
Half life?
Average time it takes for the number of unstable nuclei to halve.
Binding energy?
Energy needed to separate the nucleons in a nucleus.
Nuclear fission?
When large unstable nuclei are split into smaller daughter nuclei.
Nuclear fusion?
When two light nuclei combine to create a larger nucleus.
Moderator?
Slows down the neutrons so that they can be absorbed by the uranium nuclei.
Critical mass?
Amount of fuel needed to continue the rate of fission reaction at a steady rate.b
