Fields, photons, dynamics and electricity

Newtons law of gravitation

Every particle with mass in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres

Gravitational field

The force acting per unit mass

Coulomb’s law

Two point charges exert forces on each other. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges

Electric field at a point

The force per unit positive charge

Magnetic Flux Linkage

The product of the number of turns on the coil and the flux through the coil

Diode

A component that only allows current to flow in one direction

Lenz’s Law

The induced current flows in a direction so as to set up a magnetic field to oppose the change in magnetic flux

Faraday’s Law

The emf induced is directly proportional to the rate of change of magnetic flux

Threshold frequency

The minimum frequency of incident radiation at which electrons will be emitted from a particular metal

Work function

The minimum amount of energy needed to emit an electron from the surface of a metal

Potential Difference

The work done per unit positive charge

Current

The rate of flow of charge

Ohm's Law

Current through a conductor is directly proportional to the potential difference across the conductor at constant temperature

Resistance

A material's opposition to the flow of electric current

Emf

The total energy supplied per coulomb of charge by the cell