P3 3 - Elctromagnets Flashcards
What is the magnetic field?
The region around the magnet, in which a piece of iron or steel will be attracted.
What happens when a current flows through a wire?
A magnetic field is produced around the wire.
Where are electromagnets used?
Circuit breakers, electric bells and relays.
When is the force a maximum?
If the wire is at 90º to the magnetic field.
What is electromagnetic induction?
When a magnet is moved into a coil of wire and a potential difference is induced across the ends of the coil.
Why is there no potential difference induced when a bar magnet is held stationary inside a coil of wire?
The magnet is not cutting any field lines.
What is a transformer?
Two coils of insulated wire wound on to the same iron core.
Where and how are transformers used?
You should remember this.
P1 4.5
A transformer has 100 turns on the primary coil and 400 turns of the secondary coil. The pad across the primary coil is 2V. What is the pd across the secondary coil?
8V
