Paper 2 Definitions

Question 1

Electric potential?

Answer 1

Work done in bringing a positive charge from infinity to a distance r away from a charge Q.

Question 2

Electric potential difference?

Answer 2

Difference in electrical potential between two points in an electric field.

Question 3

Coulombs law?

Answer 3

Force between two charges is proportional to the product of the charges.

Question 4

Electric field strength?

Answer 4

Force per unit charge acting on a small positive test charge at that point.

Question 5

Capacitance?

Answer 5

Charge required to cause unit potential difference in a conductor.

Question 6

Permittivity?

Answer 6

A measure of how difficult it is to generate an electric field in a medium.

Question 7

Dielectric?

Answer 7

A material whose molecules polarise inside an electric field.

Question 8

Magnetic flux density?

Answer 8

Force on one metre of wire carrying a current of 1 amp at right angles to the magnetic field.

Question 9

Magnetic flux density?

Answer 9

Strength of the magnetic field or the number of field lines per unit area.

Question 10

Induced emf?

Answer 10

Rate of change of flux linkage.

Question 11

Faraday’s law?

Answer 11

Induced emf is directly proportional to the rate of change of flux linkage.

Question 12

Lenz’s law?

Answer 12

The induced emf is always in such a direction as to oppose the change that caused it.

Question 13

AC?

Answer 13

One that changes direction with time.

Question 14

Transformers?

Answer 14

Devices that make use of electromagnetic induction to change the size of the voltage for alternating current.

Question 15

Eddy currents?

Answer 15

Looping current induced by the changing magnetic flux, resulting in the reduction of the value of the induced emf in the secondary coil.

Question 16

Field?

Answer 16

A region where a body will experience a non-contact force.

Question 17

Gravitational fields?

Answer 17

A region of space which any mass will experience a force of attraction.

Question 18

Gravitational field strength?

Answer 18

Force per unit mass on a small test mass placed in the field.

Question 19

Gravitational potential?

Answer 19

The GPE that a unit mass at that point would have.

Question 20

Equipotentials?

Answer 20

Lines which connect points of the same gravitational potential.

Question 21

Escape velocity?

Answer 21

Minimum velocity required for an object to escape from the planet when fired vertically from the surface.

Question 22

Synchronous orbit?

Answer 22

When an orbiting object has an orbital period equal to the rotational period of the object it is orbiting.

Question 23

Internal energy of a body?

Answer 23

Sum of the randomly distributed kinetic and potential energies of all its particles.

Question 24

Specific heat capacity of a substance?

Answer 24

Amount of energy needed to raise the temperature of 1kg of the substance by 1K.

Question 25

Latent heat?

Answer 25

Energy needed to break the bonds that hold the particles in place.

Question 26

Specific latent heat of fusion or vaporisation?

Answer 26

Quantity of thermal energy needed to be gained or lost to change the state of 1kg of a substance.

Question 27

Boyle's law?

Answer 27

At a constant temperature the pressure p and volume V of a gas are inversely proportional.

Question 28

Charle's law?

Answer 28

At constant pressure, the volume V of a gas is directly proportional to its absolute temperature, T.

Question 29

Pressure law?

Answer 29

At constant volume, the pressure p of an ideal gas is directly proportional to its absolute temperature T.

Question 30

Molecular mass?

Answer 30

Sum of all the masses of all the atoms that make up a single molecule.

Question 31

Avogadro's constant?

Answer 31

Number of atoms in 12g of carbon 12.

Question 32

Molar mass?

Answer 32

Mass that 1 mole of a substance would have.

Question 33

Alpha?

Answer 33

2p, 2n, helium nucleus.

Question 34

Beta minus?

Answer 34

Fast moving electron.

Question 35

Beta plus?

Answer 35

Fast moving positron.

Question 36

Gamma?

Answer 36

High energy, high frequency, short wavelength wave.

Question 37

Intensity of radiation?

Answer 37

Amount of radiation per unit area.

Question 38

Activity?

Answer 38

Number of nuclei that decay each second.

Question 39

Decay constant?

Answer 39

Probability of a specific nucleus decaying per unit time, and is a measure of how quickly an isotope will decay.

Question 40

Half life?

Answer 40

Average time it takes for the number of unstable nuclei to halve.

Question 41

Binding energy?

Answer 41

Energy needed to separate the nucleons in a nucleus.

Question 42

Nuclear fission?

Answer 42

When large unstable nuclei are split into smaller daughter nuclei.

Question 43

Nuclear fusion?

Answer 43

When two light nuclei combine to create a larger nucleus.

Question 44

Moderator?

Answer 44

Slows down the neutrons so that they can be absorbed by the uranium nuclei.

Question 45

Critical mass?

Answer 45

Amount of fuel needed to continue the rate of fission reaction at a steady rate.b