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Think about it . .
In the space provided on page 95 answer these questions;
1. Can you change the direction of a compass without
using a bar magnet and how?
1. Can you change the strength of an electromagnet?
Magnetism from electricity
CHAPTER 16, SECTION 2
State Standard:
12.1- Recognize that electricity can be
produced using a magnet and wire coil
The Discovery of Electromagnetism
● Danish physicist Hans Christian Oersted
(UHR STED) discovered the relationship between
electricity and magnetism in 1820.
● During a lecture, he held a compass near a wire
carrying an electric current. Oersted noticed that
when the compass was close to the wire, the compass
needle no longer pointed to the north.
● The French scientist André-Marie Ampère did more
research with electricity and magnetism.
Oersted’s Experiment
Solenoids
● A solenoid is a coil of wire that produces a magnetic
field when carrying an electric current.
● In fact, the magnetic field around a solenoid is very
similar to the magnetic field of a bar magnet.
● The strength of the magnetic field of a solenoid
increases as more loops per meter are used.
● The magnetic field also becomes stronger as the
current in the wire is increased.
Electromagnets
● An electromagnet is made up of a solenoid wrapped
around an iron core.
● The magnetic field of the solenoid makes the
domains inside the iron core line up.
● The magnetic field of the electromagnet is the field of
the solenoid plus the field of the magnetized core. As
a result, the magnetic field of an electromagnet may
be hundreds of times stronger than the magnetic
field of just the solenoid.
Go to page 435 in your textbook
● Read this page and provide the appropriate
responses in your manual.
● Be prepared to share your answers.
● Can a magnet cause a current-carrying wire to move?
Explain:
YES. The electric current creates a magnetic
field that exerts a force on the wire and
causes the wire to change directions when
the current flow changes directions.
Electric Motors
DEMO
● An electric motor is a device that changes
electrical energy into mechanical energy.
● All electric motors have an armature—a loop
or coil of wire that can rotate.
● The armature is mounted between the poles
of a permanent magnet or electromagnet.
● A commutator is split half rings attached to
the ends of the armature to reverse the current
direction.
● Current enters the armature through brushes
that touch the commutator.
● Every time the armature and the commutator
make a half turn, the direction of the current
in the armature is reversed.
A Direct-Current Electric Motor
Put it together. . .
In the space in your notes answer the following;
1 – Explain how you can vary the strength of an
electromagnet
1) Increase electric current. 2) Increase the coils on a solenoid
2 – Go to page 437 in your textbook and answer
number 8.
NO. The loops must be wire not magnets. The core must
have iron in it.
Be prepared to share your answers.
Putting it Together…
●Complete the skill sheet
●It is homework due tomorrow if it
is not finished in class.