magnetism and electromagnetism Flashcards
describe how to use a plotting compass to draw a magnetic field (5)
- place a magnet on paper and draw around it
- place the plotting compass near the pole
- mark the direction of compass and then remove it and draw an arrow in that direction
- place the compass at the end of the previous arrow and repeat
- draw at least 3 full lines
how does a loudspeaker work? (6)
- AC current is constantly changing direction
- the current carrying wire is an electromagnet
- the wire feels a force from the magnet
- the force changes direction which you can see by using Fleming’s left hand rule
- this causes vibrations
- the magnets are attracted and
repelled, pushing the speaker cone in/out, making vibrations that are heard as sound.
Flemings left hand rule
what is finger is what?
thumb - force
second finger - field
middle finger - current
EMF stands for electromotive force, what does it equal to?
The potential difference (voltage) provided to a circuit
what is electromagnetic induction?
The production of a voltage by the
movement of a conductor in a
magnetic field or by the movement
or change in the magnetic field
around a conductor
A simple AC generator needs the following:
coil of wire
magnetic field
coil and field close
relative motion between coil and field
what can the voltage or current induced be increased by?
- using stronger magnets
- having more turns/coils of wire
- faster movement of the wire or magnet
how can EMF be induced in a wire?
by moving it through a magnetic field
what is an AC generator?
what is its output?
a device which converts energy from a mechanical store to an electrical store
alternating current
what does an AC generator consist of?
a coil of wire rotating in a magnetic field
slip rings and brushes
how often does the direction of the current reverse as an AC generator rotates?
the direction of the current reverses every half rotation
