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Magnetism and Electromagnetism - Coggle Diagram
Magnetism and Electromagnetism
magnets
opposite poles attract
like poles repel
magnetic materials
iron
nickel
cobalt
steel
magnetic poles are parts of a magnet that exert the
greatest force
and always come in pairs: north and south
hard and soft
magnetically hard materials are
permanent
magnets such as steel - they
retain
their magnetism
magnetically soft materials are
temporary
magnets such as iron - they
lose
their magnetism easily
induced magnetism
when
magnetic
materials are brought into a magnet's magnetic field, the magnetic material becomes a magnet with its own north and south poles
the closer the magnetic material is to the magnet, the
stronger
the induced magnetism
magnetic fields
iron fillings
show magnetic field patterns,
plotting compasses
show the field pattern and its direction
an
electric current
in a conductor produces a magnetic field around it
placing the north and south end of 2 permanent magnets near each other creates a
uniform
magnetic field pattern
magnetic field line
show the size and direction of magnetic fields
they always point from north to south
the stronger the field, the denser the field lines
a magnetic field is a volume of space where a
magnetic force
is
exerted
magnetic field patterns
see powerpoint for pictures
need to know how to draw field patterns for a straight wire, a flat circular coil and a solenoid
around a
straight wire
(with current flowing through it), the direction of the field can be found using the
right hand grip rule
a dot means current out of the page, a x means current into the page - like a dart
a
flat circular coil
also uses the
right hand grip rule
but looks like owl eyes from the top, with closer field lines between the wires and a straight line in the middle
a
solenoid
also uses the
right hand grip rule
but the field lines go from south to north inside the solenoid, and from north to south around the outside of the solenoid
electromagnets
an electromagnet consists of a
current carrying coil
wrapped around an
iron core
the magnetic field of the coil causes the magnetically soft iron core to become an
induced magnet
there is a
force
felt by a charged particle when it moves in a
magnetic field
as long as its motion is not parallel to the field
the motor effect
when a current carrying wire is placed in a
magnetic field
, the two fields
interact
with one another, causing a
force
on the wire
the direction of the force can be predicted using
Fleming's left hand rule
the thumb represents the direction of the force
the
f
irst finger as the
f
ield
the se
c
ond finger as the
c
urrent
the strength of the magnet or the current through the wire increases, so will the force felt by the wire
motors
motors create movement using the motor effect
an electric current flows around the coil of the electric motor
the magnetic field around the wire
interacts
with the field between the magnets
this produces oppositely directed forces on each side of the coil
causing it to spin
the direction of the force can be calculated using
Fleming's left hand rule
every
half revolution
the split ring commutator causes the current in the coil to reverse direction, keeping the motor spinning
loudspeakers
loudspeakers use the motor effect to produce sound waves
a.c. current is supplied to the coil of wire in the speaker
this current creates a magnetic field around the coil
this field
interacts
with the field of the permanent magnet, causing the cone of the speaker to
constantly change direction
from the a.c. current
as the cone moves, it creates
vibrations
in the air
this then creates
longitudinal sound waves
electromagnetic induction / the generator effect
if an electrical conductor
cuts
through magnetic field lines, a voltage is
induced
across the ends of the conductor
if the wire is part of a complete circuit, a
current
is induced
induced voltage increases when:
the speed of movement increases
the strength of the magnetic field increases
the number of turns of the coil increases
the area of the coil is greater
a.c. generators
as the coil is rotated,
electromagnetic induction
occurs
an
alternating voltage
is induced in the coil
this creates
alternating current
as it is in a circuit
the faster the coil rotates:
the greater the amplitude of the voltage and current
the higher the
frequency
of the a.c.