magnetism and electromagnetism Flashcards
which way do magnetic field lines point
from N to S
how can you see/ record magnetic fields
use iron filings
put the magnets under a piece of paper
put iron filings on top of the paper
tap the paper until it forms a clear pattern
how is magnetism induced
bring a magnet to a magnetic material
the closer the magnet, the stronger the induced magnetism
what does an electric current in a conductor produce
a magnetic field around it
what is a hard or soft magnet
soft: loses its induced magnetism quickly eg iron
hard: keeps its magnetism permanently eg steel
describe the motor effect
when a current carrying wire is put between magnetic poles, the two magnetic fields affect one another
the result is a force on the wire
the causes the wire to move
what is fleming’s left hand rule
First finger = field
seCond finger = Current
thuMb = motion (force)
what 4 factors speed up a simple electric motor
1) more current
2) more turns on the coil
3) stronger magnetic field
4) soft iron core
how do loudspeakers work
motor effect:
1) a.c. electric signals are fed to a coil of wire wrapped around the base of a cone
2) the coil is surrounded by a permanent magnet so the current causes a force on the coil and make it move back and forth
3) these movements make the cone vibrate, creating sound
what does a split ring commutator do
swaps the contacts every half turn to keep the motor rotating in the same direction
what is electromagnetic induction
A potential difference can be induced in a conductor when there is movement between the conductor and a magnetic field
what are the two ways where electromagnetic induction can occur
a coil of wire is moved in a magnetic field
a magnet is moved into a coil of wire
