Magnetism and Electromagnetism Flashcards
what is a magnetic field
the region of space around a magnet where a magnetic material will experience a force
where is the magnetic field of a magnet strongest
at the poles
in which direction do magnetic field lines always point
north to south
what does the distance between magnetic field lines indicate
strength of the field, closer together = stronger field
what is a permanent magnet
material that produces its own magnetic field
what is an induced magnet
material that becomes magnetic when is put in a magnetic field
what does a magnetic compass contain
small bar magnet
what is produced around a wire when an electric current flows through it
magnetic field
what factors does the strength of the magnetic field around a straight wire depend upon
size of current, distance from wire
what effect does shaping the wire into a solenoid have on the magnetic field strength
increases strength of magnetic field
how can the strength of the magnetic field inside a solenoid be increased
put an iron core inside
what does Flemmings left hand rule show
relative orientation of the force, current in the conductor, and magnetic field for the motor effect
what is magnetic flux density measured in
Tesla
what is the motor effect
when a conductor placed in a magnetic field experiences a force
what causes the motor effect
interaction between the magnetic field created by current in a wire and the magnetic field in which he wire is placed
what do loudspeakers and headphones do
use the motor effect to convert variations in current in electrical circuits to pressure variations in sound waves
2 ways that a p.d is induced in a conductor
- conductor moving relative to a magnetic field
- magnetic field around conductor changing
what is another name for the generator effect
electromagnetic induction
how can the direction of an induced p.d or current be reversed
- reverse movement of the conductor or magnet
- reverse polarity of the magnet
what affects the size of an induced p.d or current
- speed of movement
- strength of the magnetic field
- number of turns in the coil
how does an alternator make use of the generator effect
produces alternating current
which kind of current is produced buy the generator effect in a dynamo
direct current
how does a dynamo keep the current flowing in the same direction
a split ring commutator makes the ends of the coil swap contacts with the circuit every half turn
when is the induced p.d produced by an alternator at its maximum
when the plane of the coil lies parallel to magnetic field lines
how does a microphone use the generator effect
converts pressure variations in sound waves into variations in electrical current
what does a transformer do
changes magnitude of the alternating p.d
what does a basic transformer consist of
two coils of wire wound around an iron core
why is iron used for the core of a transformer
iron is easily magnetised and demagnetised
how does a transformer work
alternating p.d across the primary coil produces an alternating magnetic field in the iron core which induces an alternating p.d in the secondary coil
which type of transformer has more turns on its secondary coil than its primary coil
step up
