Download Section 22.2 - CPO Science

ELECTRICITY AND MAGNETISM 22.2
Chapter Twenty-Two: Electricity
and Magnetism
22.1 Properties of Magnets
22.2 Electromagnets
22.3 Electric Motors
Chapter 22.2 Learning Goals
Define electromagnet.
Build a simple electromagnet.
Compare permanent magnets and
electromagnets.
Investigation 22B
Electromagnets
Key Question:
How are electricity and magnetism related?
22.2 Electomagnets
Electromagnets are
magnets that are created
when there is electric
current flowing in a wire.
The simplest
electromagnet uses a coil
of wire wrapped around
some iron.
22.2 Right hand rule
To find the north pole
of an electromagnet,
use the right hand rule.
When the fingers of
your right hand curl in
the direction of the
wire, your thumb points
toward the magnet’s
north pole.
22.2 Electromagnets in Toasters
By changing the
amount of current,
you can easily
change the strength
of an electromagnet
or even turn its
magnetism on and
off.
A toaster tray is
pulled down by an
electromagnet while
bread is toasting.
22.2 Doorbells
A doorbell contains
an electromagnet.
When the button of
the bell is pushed, it
sends current
through the
electromagnet.
22.2 Building an electromagnet
You can easily build
an electromagnet
from wire and a
piece of iron, such
as a nail.
Wrap the wire in
many turns around
the nail and connect
a battery.
22.2 Building an electromagnet
 There are two ways to
increase the current in a
simple electromagnet:
1. Apply more voltage by
adding a second battery.
2. Add more turns of wire
around the nail.
Why do these two
techniques work?
22.2 Similarities in permanent
and electromagnets
 The charged electrons in atoms
behave like small loops of current.
 Electric current through loops of
wire creates an electromagnet.
 Atomic-scale electric currents
create a permanent magnet.
22.2 Magnetic materials
 Atoms act like
tiny magnets.
Permanent magnets have
their atoms aligned,
creating the magnetic
forces we observe.
22.2 Magnetic materials
 In iron, the atoms are free to rotate
and easily align their individual
north and south poles.
22.2 Nonmagnetic materials
 The atoms in
non-magnetic
materials, like
plastic, are not
free to move or
change their
magnetic
orientation.