Topic 7 - Magnetism and electromagnetism Flashcards
how does a transformer work
A transformer consists of an iron core with a coil on either side, the electricity isnt conducted through the core since the wires are insulated.
When supplied with an alternating current, the primary coil will generate an alternating magnetic field.
This then induces an alternating magnetic field in the iron core.
This in turn induces an alternating voltage in the secondary coil, which if the circuit is complete will lead to an alternating current
the primary coil has less turns than the secondary coil in a step up transformer V.V
how does a dynamo work
a Dynamo produces Direct current since it uses a split ring commutator
As the coil rotates, it cuts through the field lines
This induces a potential difference between the end of the coil
The split ring commutator changes the connections between the coil and the brushes every half turn to keep the current leaving the dynamo in the same direction
This happens each time the coil is perpendicular to the magnetic field lines
Therefore, the induced potential difference does not reverse its direction as it does in the alternator
Instead, it varies from zero to a maximum value twice each cycle of rotation, and never changes polarity (positive to negative)
This means the current is always positive (or always negative)
how does an alternator work
Alternator produces alternating current since the direction of the current changes each half turn with the coil since it is
A rectangular coil that is forced to spin in a uniform magnetic field
The coil is connected to a centre-reading meter by metal brushes that press on two metal slip rings/ commutator rings - the brushes connects the circuit to the wires which are connected to the slip rings , one side of wire connected to one slip ring
The slip rings and brushes provide a continuous connection between the coil and the meter
When the coil turns in one direction:
The pointer on current meter defects first one way, then the opposite way, and then back again
This is because the coil cuts through the magnetic field lines and a potential difference, and therefore current, is induced in the coil
This is because the induced potential difference in the coil repeatedly changes its direction
This continues on as long as the coil keeps turning in the same direction
The induced potential difference and the current alternate because they repeatedly change direction
