Transcript magnetic domain

Magnetism and
Electromagnetism
Magnets and Electromagnetism
Georgia Performance Standards
SPS10. Students will investigate the of properties
electricity and magnetism.
c. Investigate applications of magnetism and/or its
relationship to the movement of electrical charge as it
relates to
electromagnets
simple motors
permanent magnets
How were magnets discovered?
• Magnetite/Lodestone = naturally
occurring mineral
• Could pick up metallic objects
• If floated on water, it would always
orient itself in the same direction
The magnetic force…
(notes)
• Is an interaction between two magnets
• can even be felt before magnets touch
• gets stronger as the magnets get closer
What is a magnetic field?
• a field that
(notes)
– surrounds a magnet and exerts magnetic
force
– connects the north and south poles of a
magnet together
How do magnets interact?
(notes)
• opposite poles (N,S) attract each other
• like poles (N, N or S,S) repel each other
Earth is a giant magnet
• Earth’s geographic north pole (GNP) is
its magnetic south pole (MSP)
– the “north” needle on a compass points
toward the GNP because it’s really the
MSP!
(notes)
What makes something magnetic?
• magnetic domain = groups of atoms with
aligned magnetic poles
-- unaligned magnetic domains = nonmagnetic
-- aligned magnetic domains = magnetic
(notes)
How can magnets be “demagnetized?”
• heating
• jarring
– hitting
– dropping
• both cause the magnetic domains to
move around and become unaligned
demagnetized magnets can be
re-magnetized by exposing them to a
very strong magnetic field
(notes)
What happens if you cut a
magnet in to 2 pieces?
S
N
break in two
S
N
S
N
What is an
electromagnet?
(notes)
• Temporary magnet
• Made by placing a piece of metal inside
a current-carrying wire
• Temporarily aligns magnetic domains
How can the strength of an
electromagnet be increased?
1. add more coils of wire
2. increase the electric current through
the wire
Benefits of Electromagnets
(versus Permanent Magnets)
1. Turn on and off
2. Control the strength
Examples of Ways
Electromagnets are used are…
• Look at the following slides and know
how each work… especially the
relationship between the permanent
magnets and electromagnets to make it
move (if they have them…)
• What are the two main parts of an
electric motor? Permanent magnet and
electromagnet.
galvanometer
magnets
It is possible to…
(notes)
• produce an electric current by moving a loop
•
of wire through a magnetic field
This is called ELECTROMAGNETIC
INDUCTION.
• Main example of Electromagnetic Induction in
action is a
– generator: produces electricity by rotating a coil
of wire in a magnetic field
Other Examples of Uses: Hydroelectric dam,
windmill, shake flashlight, winding flashlight