6.3 Definitions OCR A A Level Physics

Faraday’s Law

The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux linkage.

Field Lines

Lines that show the direction in which a magnetic North monopole would experience a force if placed at that point in a field. Magnetic field lines point from North to South.

Fleming’s Left-Hand Rule

The relative direction of motion, field direction, and current direction in the motor effect can be represented by the thumb, first finger, and second finger of the left hand respectively. For a charged particle in a magnetic field, its direction replaces the current direction.

Force on a Charged Particle

A charged particle moving through a magnetic field experiences a force equal to the product of the charge, its velocity, and the magnetic flux density.

Force on a Current-Carrying Conductor

A current-carrying conductor experiences a force when placed in a magnetic field. The direction of the force can be determined using Fleming’s left-hand rule.

Lenz’s Law

The direction of an induced current is such that it opposes the current that created it.

Magnetic Field

A region of space in which magnetic materials and moving electric charges feel a force.

Magnetic Flux Density

The force per unit current per unit length on a current-carrying wire placed at 90° to the field lines. Also known as magnetic field strength.

Magnetic Flux Linkage

The magnetic flux multiplied by the number of turns, N, of the coil.

Magnetic Flux

A value that describes the magnetic field or field lines passing through an area. It is the product of magnetic flux density and the perpendicular area it passes through.

Tesla

The unit of magnetic flux density.

Transformer

A device that increases or decreases voltage using two sets of coils with different numbers of turns around a magnetic core. Step-up: more turns on secondary coil. Step-down: fewer turns on secondary coil.

Velocity Selector

A combination of a magnetic field and an electric field that allows only charges with a specific velocity to pass through undeflected.

Weber

The unit of magnetic flux.