Flashcards in Definitions Deck (96)

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31

## Ohm's Law

### The current flowing through a metallic conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant

32

## Resistivity

### The resistance of a piece of wire 1m in length and with a cross sectional area of 1m^2

33

## Centre of mass

### The point through which a single force on the body has no turning effect

34

## Principle of conservation of linear momentum

### The total linear momentum of a system of interacting bodies is constant, providing no external forces act

35

## Work function

### Minimum energy to liberate electron

36

## Excitation

### When an electrion takes in energy from a photon or collision and goes up an energy level

37

## Ionisation

### When an electron takes in enough energy to leave the atom

38

## Progressive waves

### Waves that move outwards from their source

39

## Transverse waves

### Each particle oscillates perpendicular to the direction of propagation to the wave

40

## Longitudinal wves

### Each particle oscillates parallel to the direction of propagation to the wave

41

## Rarefied

### More distance between particles than usual

42

## Compression

### Particles closer together

43

## Mechanical waves

### Oscillation of particles in a physical medium

44

## Refraction

### Change in path of light ray caused by a change in speed

45

## Total internal reflection

### The angle of incidence is greater than the critical angle

46

## Diffraction

### The spreading of waves when passed through a gap or round an obstacle

47

## Kirchhoff's First Law

### The sum of the currents leaving any junction is always equal to the sum of the currents that entered it

48

## Kirchhoff's Second Law

### The sum of potential differences across components of a series circuit is equal to the emf

49

## Internal Resistance

### Resistance inside a source of electrical energy; the loss of pd per unit current in the source when current passes through it

50

## Potential Divider

### Two or more resistors in series connected to a source of pd

51

## Superconductor

### A material that has zero electrical resistance below a critical temperature.

52

## Gravitational Field Strength

### The force per unit mass acting on a small test mass placed in the field

53

## Gravitational Potential

### The work done to move a unit mass from infinity to that point in a gravitational field

54

## Kepler's First Law

### All planets move about the Sun in elliptical orbits, having the Sun as one of the foci

55

## Kepler's Second Law

### A radius vector joining any planet to the sun, sweeps out equal areas in equal lengths of time

56

## Kepler's Third Law

### The square of the period of a planet's orbit is proportional to the cube of the mean radius of its orbit

57

## Coulomb's Law

### The magnitude of the force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance between them

58

## Electric Field

### Region where a charged particle will experience a force

59

## Gravitational Field

### The region surrounding an object in which it exerts a gravitational force on any other object

60