Transcript Document

UNIT FIVE: Electricity and Magnetism
 Chapter 16 Electricity
 Chapter 17 Magnetism
Chapter Seventeen: Magnetism
 17.1 Properties of Magnets
 17.2 Electromagnets
 17.3 Electric Motors and Generators
 17.4 Generating Electricity
Chapter 17.2 Learning Goals
 Define electromagnet.
 Build a simple electromagnet.
 Compare permanent magnets and
electromagnets.
Investigation 17B
Electromagnets
 Key Question:
How are electricity and magnetism related?
17.2 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.
17.2 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.
17.2 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.
17.2 Doorbells
 A doorbell contains an
electromagnet.
 When the button of the
bell is pushed, it
sends current through
the electromagnet.
17.2 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.
17.2 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?
17.2 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.
17.2 Magnetic materials

Atoms act like tiny
magnets.
Permanent magnets have
their atoms aligned,
creating the magnetic
forces we observe.
17.2 Magnetic materials

In iron, the atoms are free to rotate and
easily align their individual north and
south poles.
17.2 Nonmagnetic materials

The atoms in nonmagnetic
materials, like
plastic, are not free
to move or change
their magnetic
orientation.