Ch21 Electromagnetic Induction Flashcards
Define induced e.m.f./ induced voltage:
The e.m.f. created in a conductor when it cuts through magnetic field lines
Define electromagnetic induction:
The production of an e.m.f
across an electrical conductor
when there is relative movement
between the conductor and a magnetic field
Define Flemings right-hand rule:
A rule that gives the relationship
between the directions of force, field and current
when a current flows across a magnetic field
Define a.c. generator:
A device such as a dynamo
used to generate alternating current
Define slip rings:
A device used to allow current to flow to and from the coil of an a.c. generator
Define Lenz’s law:
The direction of an induced current
always opposes the change in the circuit/the magnetic field
that produces it
Define power lines:
Cables used to carry electricity from power stations to consumers
Define national grid:
The system of powerlines, pylons and transformers used to carry electricity around the country
Define transformer:
A device used to change voltage of an a.c. electricity supply
Define primary coil:
The input coil of a transformer
Define secondary coil:
The output coil of a transformer
Define step-up transformer:
A transformer which increases the voltage of an a.c. supply
Define step-down transformer:
Transformer which decreases the voltage of an a.c. supply
What is the transformer equation?
Voltage across primary coil/voltage across secondary coil = number of turns on primary/number of turns on secondary
Vp/Vs = Np/Ns
What is the equation for power loss?
Power loss = square of current in the cable x resistance
P = I²R
