Definitions

Question 1

electric current

Answer 1

the rate of flow of electric charge

Question 2

p.d.

Answer 2

the p.d. between two points is the energy converted from electrical potential energy into some other form per coulomb of charge

Question 3

ohms law

Answer 3

the current flowing through a wire at a constant temperature is proportional to the p.d. across it

Question 4

electrical resistance

Answer 4

the resistance of a conducted is the p.d. across it divided by the resulting current

Question 5

resistivity, P

Answer 5

the resistance, R, of a metal wire of length, L, and cross sectional area, A, is given by R=PL÷A in which P, the resistivity is a constant (at a constant temperature) for the material of the wire

Question 6

superconducting transition temperature

Answer 6

the temperature at which a material when cooled loses all its electrical resistance and becomes superconducting

Question 7

law of conservation of charge

Answer 7

electric charge cannot be created or destroyed, though positive and negative charges can neutralise each other. charge cannot pile up anywhere

Question 8

e.m.f

Answer 8

the e.m.f of a source is the energy converted from some other form (e.g. chemical) to electrical potential per coulomb of charge flowing through the source

Question 9

progressive wave

Answer 9

a pattern of disturbances travelling through a medium and carrying energy with it, involving the particles of the medium oscillating about their equilibrium positions

Question 10

transverse wave

Answer 10

a transverse wave is one where the particles oscillations are at right angles to the direction of travel of the wave

Question 11

longitudinal wave

Answer 11

a longitudinal wave is one where the particles oscillations are parallel to the direction of travel of the wave

Question 12

polarised wave

Answer 12

a polarised wave is a transverse wave in which the particle oscillations occur in only one of the directions at right angles to the direction of the movement of the wave

Question 13

wavelength of a progressive wave

Answer 13

the minimum distance between two points on the wave oscillating in phase

Question 14

frequency of a wave

Answer 14

the number of cycles of a wave that pass a given point in one second

Question 15

the principle of superposition

Answer 15

the principle of superposition states that if waves from two sources occupy the same space then the total displacement at any one point is the vector sum of the individual displacements

Question 16

in phase

Answer 16

waves arriving at a point are said to be in phase if they have the same frequency and are at the same point in their wave cycle.

Question 17

phase difference

Answer 17

phase difference is the difference in position of 2 points within a cycle of oscillation. one cycle = 360 degrees or 2 pi

Question 18

quantity

Answer 18

a quantity is represented by a number x a unit

Question 19

Scalar

Answer 19

a scalar is a quantity with magnitude only

Question 20

vector

Answer 20

a vector is a quantity with both direction and magnitude

Question 21

force

Answer 21

a force on a body is a push or pull acting on the body from an external force

Question 22

newton’s third law

Answer 22

if body A exerts a force on body B then body B will exert and equal and opposite force on body A

Question 23

sigma F=MA (newton’s second law)

Answer 23

the mass of a body x it’s acceleration is equal to the vector sum of the forces acting on the body. this vector sum is called the resultant force

Question 24

density of a material

Answer 24

density is an objects mass÷volume

Question 25

moment of a force

Answer 25

the moment of a force about a point is defined as the force x the perpendicular distance from the point to the line of action of the force

Question 26

the principle of moments

Answer 26

for a system to be in equilibrium the moment clockwise must be equal to the moment anticlockwise

Question 27

centre of gravity

Answer 27

the centre of gravity is the point within a body at which we can consider all the weight is acting upon

Question 28

displacement

Answer 28

the displacement of point B from point A is the shortest distance from A to B with the direction

Question 29

work

Answer 29

the work done by a force is the product of the magnitude of the force and the distance moved in the direction of the force

Question 30

energy

Answer 30

the energy of a body or system is the amount of work it can do

Question 31

principle of conservation of energy

Answer 31

energy cannot be created or destroyed, only transferred from one form to another. energy is a scalar

Question 32

potential energy

Answer 32

potential energy is energy possessed by virtue of position

Question 33

kinetic energy

Answer 33

kinetic energy is energy possessed by virtue of its motion

Question 34

power

Answer 34

power is the work done per second or energy transferred per second

Question 35

isotope

Answer 35

isotopes are atoms with the same number of protons but different number of neutrons in the nuclei

Question 36

momentum

Answer 36

the momentum of an object is its mass multiplied by its velocity