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.