Download Electromagnets! - ScienceStLaurence

Electromagnets!
By Jack and Bella
These are
products where
electric
magnets are
used in them!
Electric
bells!
Electric bells like the ones used in
most schools also contain an
electromagnet.
When the current flows through
the circuit, the electromagnet
makes a magnetic field.
The electromagnet attracts the
springy metal arm.
The arm hits the gong, which
makes a sound.
The circuit is broken now the arm
is out of position.
The electromagnet is turned off
and the springy metal arm moves
back.
The circuit is complete again.
The cycle repeats as long as the
switch is closed. Check your
understanding of this with the
animation.
Loud
speakers!
The most common type of
loudspeaker is the MOVING COIL
speaker, where a coil of wire is
suspended in the magnetic field of
a circular magnet.
When a speech current is passed
through the coil a varying magnetic
field is generated by the coil.
The two magnetic fields interact
causing movement of the coil.
The movement of the coil causes a
cone, which is attached to the coil, to
move back and forth.
This compresses and decompresses
the air thereby generating sound
waves.
The loudspeaker is a TRANSDUCER
converting one form of energy to
another.
Lifting
magnets!
All industrial lifting magnets
are electromagnets. From the
outside, you see only a heavy
cast or machined steel casing
and a cover plate. Inside is a
winding aluminium or copper
electrical conductor. Each
layer of the coil is separated
by a thin layer of insulation.
The inside of the casing is also
coated with insulation. The
cover plate is a sheet of
manganese, providing an
extremely hard, non-magnetic
protective shield for the coils.
The final component is a
cable carrying 230 volts of DC
current.
Energized
door locks!
An electric door lock includes a
handle rotatable attached to a
housing, a lock device engaged
in the housing, a follower
rotatable secure the handle to
the housing, an
electromagnetic control device
having a receptacle rotatable
received in the follower, a
plunger slidably engaged in the
receptacle and extendible out
of the receptacle to engage
with the follower, and a
latching device for selectively
latching the plunger to the
receptacle. The plunger may be
selectively actuated to engage
with the follower either by the
lock device and correct keys or
by the electromagnetic control
device with correctly entered
passwords or secret codes.
Relays!
All relays contain a sensing unit,
the electric coil, which is
powered by AC or DC current.
When the applied current or
voltage exceeds a threshold
value, the coil activates the
armature, which operates either
to close the open contacts or to
open the closed contacts. When
a power is supplied to the coil, it
generates a magnetic force that
actuates the switch mechanism.
The magnetic force is, in effect,
relaying the action from one
circuit to another. The first circuit
is called the control circuit; the
second is called the load circuit.