P4 Magnetism Flashcards
What happens when you move an induced magnet away from a permanent magnet?
It loses its magnetism
Why do compasses point north when they aren’t near a magnet?
The Earths core generates a magnetic field and the needles of compasses line up with it.
What can you use to show there is a magnetic field around a straight current carrying wire?
A compass
How would you increase magnetic effect at the ends of a solenoid?
- increase current in the wire
- increase number of coils while keeping length of solenoid the same
- shorten solenoid with same number of coils
- add an iron core inside the solenoid
How would you increase magnetic field strength around a current carrying wire?
Increase current
State what each finger represents in Flemmings left hand rule.
Thumb- direction of force
First finger- magnetic field direction
Second finger- current direction
Why might a current carrying wire move when placed between magnetic poles?
The magnetic field around the wire interacts with the magnetic field between the poles. The result is a force experienced by the wire that can cause the wire to move.
What type of current must be supplied to a loudspeaker for it to work?
Alternating current
What does a split ring commutator do?
It swaps the positive and negative terminal of a coil every half turn.
Give two ways that you can reverse the direction of a basic d.c. motor.
- reverse the current
- swap the magnetic poles over
What is electromagnetic induction?
When a potential difference is induced across a conductor when it experiences a change in an external field.
Describe how a potential difference in a wire can be induced using a magnetic field.
Move the wire relative to the magnetic field, or change the magnetic field the wire is in.
