Transcript Magnetism from Electricity

Magnetism from Electricity
Did you know?
Most trains you see roll
on wheels on top of a
track. But engineers
have developed trains
with no wheels that
FLOAT above the track!
These trains are able to
levitate because of
magnetic forces
between the track and
the train cars.
Magnetism from Electricity
• Danish physicist
Hans Christian
Oersted
discovered the
relationship
between
electricity and
magnetism in
1820.
Magnetism from Electricity
• A magnetic needle
balances on the
central rod. The two
end posts support a
metal wire. Each end
of the wire extends down
through the wooden posts and is connected
to a small metal post in the base. When one
metal post was connected to the positive
pole of a battery and the other metal post
was connected to the negative pole of a
battery, current would flow in the wire. The
needle would then swing until it was at right
angles to the wire.
Magnetism from Electricity
• French scientist Andre-Marie
Ampere heard about Oersted’s
findings and did more research.
Together their work was the first
research conducted on
electromagnetism.
• Electromagnetism is the
interaction between electricity
and magnetism.
Magnetism from Electricity
• Although the magnetic field
created by an electric current in
a wire may deflect a compass
needle, it is not strong enough to
be very useful.
• Two devices, the solenoid and
the electromagnet, strengthen
the magnetic field enough to be
useful.
Magnetism from Electricity
• A solenoid is a coil of wire that
produces a magnetic field when
carrying an electric current.
Magnetism from Electricity
• The strength of
the magnetic field
increases as more
loops of wire are
added and as the
current in the wire
is increased.
Magnetism from Electricity
• An electromagnet is a
magnet that consists
of a solenoid wrapped
around an iron core.
The magnetic field
produced by the
solenoid causes the
domains in the iron to
become better
aligned.
Magnetism from Electricity
• An electric motor is a device
that changes electrical energy
into kinetic energy.
• All electric motors have an
armature, a loop or coil of wire
that can rotate. The armature is
mounted between the poles of a
magnet.
Magnetism from Electricity
• A simple DC
electric motor.
When the coil is
powered, a
magnetic field is
generated around
the armature. The
left side of the
armature is pushed
away from the left
magnet and drawn
toward the right,
causing rotation.
Magnetism from Electricity
• The armature
continues to
rotate
Magnetism from Electricity
• When the armature
becomes horizontally
aligned, the
commutator reverses
the direction of
current through the
coil, reversing the
magnetic field. The
process then repeats.
Magnetism from Electricity
• A galvanometer
is a device used
to measure
current through
the interaction
of an
electromagnet
and a permanent
magnet.