Topic D Definitions

Definitions for topics D1-D4 (only 4,5 ratings), bold most important parts of each definition, extra notes partially missing, SL & HL

Gravitational potential (v)

Work done per unit mass in moving a small point mass from infinity to a point

Gravitational potential energy (ep)

The work done in moving a mass from infinity to a point

Equipotential surfaces

Set of points that have the same potential

At right angles to field lines

Escape speed

The minimum speed at launch (or without further energy input) from a point in a gravitational field such that a particle can travel to infinity and never return

Gravitational field strength

The gravitational force per unit mass experiencedby a small point mass

Kepler’s Third Law

The ratio of the orbital period squared to the average orbital radius cubed is constant for all planets

Gravitational force acts on…

… all particles with mass

Kepler’s First Law

The orbit of a planet is an ellipse with the Sun at one of the two foci

Kepler’s Second Law

A line segment joining a planet and the Sun sweeps out equal areas in equal times

Electric potential (V)

Work done per unit charge moving a small positive test charge from infinity to a point in an electric field

Electric potential energy

The work that needs to be done by an external agent in order to assemble a system of charges from infinite separation

Electric field strength

Electric force per positive unit test charge (E = F/q)

Millikan’s oil drop experiment

Showed the quantisation of electric charge

Found that charge on oil drops was in multiples of 1.6×10^-19

Electronvolt (eV)

Energy gained by an electron moving through an electric potential difference of one volt (OR: Work done moving an electron through an electric potential difference of one volt)

Path of a charged particle in a uniform electric field

Parabolic

Path of a charged particle in a uniform magnetic field

If motion is perpendicular to magnetic field: circular path

If motion is parallel to magnetic field: undeflected - straight line

If motion is at another angle to magnetic field: helical path

Path of a charged particle in perpendicular magnetic and electric fields

This is a velocity selector

All undeflected particles will have the same velocity

(F(E)=F(M), so qE = Bqv, so v= E/B)

Direcction of force on parallel current-carrying wires

Currents in same direction attract

Currents in opposite directions repel

(For currents, like currents attract unlike charges/poles)

Lenz’s law

Induced emf/induced current acts so as to oppose the change causing it

This is a consequence of conservation of energy

(OR: The direction of an induced emf is such that it produces a magnetic field whose direction opposes the change that produced it)

Increasing frequency of rotation of generator

1. Reduced period of induced emf

2. Increases magnitude of induced emf

Faraday’s law

The induced emf in a loop is the rate of changed of magnetic flux linkage through the loop