Physics · Paper 2

Magnetism and electromagnetism

Permanent and induced magnets, magnetic fields, electromagnetism, the motor effect, electric motors, loudspeakers, the generator effect, alternators and dynamos, microphones and transformers.

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Key terms in this chapter

All 48, gathered from every lesson.

Electromagnet
A solenoid with an iron core that is magnetic only when a current flows.
Solenoid
A coil of wire.
Magnetic field
The region around a magnet or current where a force acts on magnetic materials.
Current
The rate of flow of charge.
Core
A piece of iron inside a solenoid.
Turns
Loops of wire in a coil.
Motor effect
The force on a current-carrying conductor in a magnetic field.
Magnetic flux density
A measure of the strength of a magnetic field, in tesla (T).
Tesla
The unit of magnetic flux density.
Fleming's left-hand rule
A rule for finding the direction of the force on a current-carrying wire in a magnetic field.
Conductor
A material that allows a current to flow.
Thumb
Gives the direction of the force in Fleming's left-hand rule.
d.c. motor
A motor that uses direct current to make a coil rotate in a magnetic field.
Commutator
A split ring that reverses the current each half turn.
Brushes
Carbon contacts that touch the commutator.
Coil
A loop of wire that turns in the magnetic field.
Rotation
Turning about an axis.
Motor effect
The force on a current-carrying wire in a magnetic field.
Loudspeaker
A device that uses the motor effect to convert electrical signals into sound.
Cone
The part of the loudspeaker that vibrates to make sound.
Alternating current
A current that repeatedly changes direction.
Frequency
The number of vibrations each second.
Amplitude
The size of the vibration.
Diaphragm
A thin vibrating membrane.
Generator effect
The induction of a potential difference across a conductor when the magnetic field changes or the conductor moves in a magnetic field.
Induced potential difference
A p.d. produced by the generator effect.
Induced current
A current produced in a complete circuit by an induced p.d.
Coil
Loops of wire.
Flux
The magnetic field passing through a coil.
Galvanometer
A sensitive meter that shows small currents.
Alternator
A generator that produces alternating current.
Dynamo
A generator that produces direct current.
Slip rings
Rings that keep the coil connected to the brushes without reversing the output.
Commutator
A split ring that reverses the connections each half turn.
Microphone
A device that converts sound into an electrical signal.
Brush
A carbon contact that touches a ring.
Transformer
A device that changes the potential difference of an alternating supply.
Primary coil
The input coil of a transformer.
Secondary coil
The output coil of a transformer.
Step-up transformer
A transformer that increases the potential difference.
Step-down transformer
A transformer that decreases the potential difference.
Soft iron core
A core that easily becomes magnetised and demagnetised, linking the coils.
Magnetic pole
The end of a magnet where the force is strongest.
Magnetic field
The region around a magnet where a force acts on another magnet or a magnetic material.
Permanent magnet
A magnet that always produces its own magnetic field.
Induced magnet
A material that becomes magnetic only when in a magnetic field.
Field line
A line showing the direction of the force on a north pole.
Compass
A small magnet that lines up with a magnetic field.