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Key Idea: Moving
charges (like those in an electric current) produce a magnetic field
·
A circular filed is formed around a wire
·
It depends on the
direction of current
· The strength
of the field depends on the current
in the wire
Electromagnet—a temporary magnet made by placing a piece of iron
inside a current carrying wire
·
The magnetic
field is only present when current is flowing in the wire
·
Increase magnetic
field by:
o
adding more
turns to the wire coil
o
increasing
current through the wire
· A galvanometer
is an electromagnet that is used to detect an electric current
Electric motor—a device the changes electrical energy into mechanical energy
·
It has an
electromagnet (wire coil) that is free to rotate between the poles of a
permanent magnet
·
When current
flows in the wire coil, a magnetic field is produced
·
Changing
direction of the current (alternating current) causes the coil to keep rotating
(it pushes away from the permanent magnet)
·
Rotation speed of
the motor can be controlled by changing the amount of current in the coil
o
When there is
more current, the magnetic field is stronger, the force between the
electromagnet and the permanent magnet increases, and the coil turns faster
