force on a conductor (at right angles to a magnetic field) carrying a current (N) = magnetic field strength (T) × current (A) × length (m)
potential difference across primary coil (V)/potential difference across secondary coil (V) = number of turns in primary coil/number of turns in secondary coil
potential difference across primary coil (V) × current in primary coil (A) = potential difference across secondary coil (V) × current in secondary coil (A)
Magnetic Field / Magnetic Flux - an area of space in which a magnetic object would have a force exerted on it.
Magnetics Field Lines - a representation of the field as arrows which point from magnetic north poles to south. The closer the lines are together the stronger the field at that point.
Permanent Magnet - a ferromagnetic object, (i.e. iron, cobalt or nickel), which always has a magnetic field around it.
Induced Magnet - a temporary magnetic object due to a magnetic material being in a magnetic field.
Domain Theory - a way of visualising magnetic materials as being many smaller magnets. Normally these “domains” are randomly orientated, when magnetised they line up with one another.
Compass - a freely rotating magnet which lines up with Earth’s magnetic field.
Magnetic North Pole - the point on the earth towards which a north seeking (south) pole of a compass would point.
Magnetic Field Strength / Magnetic Flux Density - a measure of the magnitude of force that a magnet can exert on a magnetic object. Has units Tesla (T).
Solenoid - a coil of conducting wire. When a current is passed through it has a similar shaped field to a bar magnet.
Electromagnet - a temporary magnet caused by a current being switched on or off.
The motor effect - a force being produced on a current carrying conductor when its magnetic field interacts with a permanent magnetic field at right angles.
Fleming’s Left Hand Rule - a rule used to determine the direction of a force on a current carrying conductor in a magnetic field. The thumb represents the force, the first finger represents the magnetic field and the second finger represents the current.
Motor - a device which rotates as the direction of the force is always in the same rotating direction. Consists of a rotating coil of wire, a permanent magnetic field and a split-ring commutator.
Split-ring Commutator - a device which allows a DC input to change connectors every half rotation of the coil of wire every half rotation, this keeps the force in the same rotating direction.
Electromagnetic Induction - a voltage is induced across a conductor within a changing magnetic field. Can also be caused by relative motion between conductor and magnetic field.
Induced Potential Difference
Alternating Potential Difference - a potential difference which constantly switches from a positive direction to a negative direction.
Alternating Current - a current which constantly switches from a positive direction to a negative direction.
Alternator / Generator - a device which induces an alternating voltage due to a coil of wire spinning in magnetic field. Consists of a rotating coil of wire, a permanent magnetic (or stator coils) field and a slip ring and brushes apparatus.
Slip-rings - two rings which allow the brush connectors to the coil of wire to slip around them as the generator rotates.
Dynamo - a generator which produces DC voltage by using a split-ring commutator instead of slip-rings and brushes. Is essentially a motor in reverse.
Transformer - a device which uses an alternating current in a primary coil to create a changing magnetic field in a laminated soft iron core which then induces a changing voltage in a secondary coil. Can be used to isolate circuits and to change (transform) voltages.
Step-up transformer - a transformer with more coils on the secondary (output) coil than on the primary (input) coil. The voltage output is greater than the voltage input.
Step-down transformer - a transformer with fewer coils on the secondary (output) coil than on the primary (input) coil. The voltage output is less than the voltage input.
Microphone - a device which turns a sound wave into an electrical signal by means of the wave causing diaphragm to oscillate, the diaphragm is attached to a magnet which moves within a coil of wire.
Loud Speaker - a device which turns an electrical signal into a sound wave by means of the signal causing a magnet to oscillate within a coil of wire, the magnet in turn oscillates a speaker cone.