Transcript What is an ELECTROMAGNET?

What is Electromagnetism?
•It is the INTERACTION
between ELECTRIC
CURRENTS and
MAGNETIC FIELDS.
•It is when a moving
CHARGE creates an
ELECTROMAGNETIC
FIELD.
What is an ELECTROMAGNET?
• When an electric current
is passed through a coil
of wire wrapped around
a metal core, a very
strong magnetic field is
produced This is called
an electromagnet.
Electromagnets are Created By:
• SOLENOID: A current
flowing through a coil of
wire.
• Putting an iron core or
magnet in the middle of
the coil of wire increases
the strength of the
electromagnet’s magnetic
field.
Find the direction of the magnetic field
using the RIGHT hand grip rule!
•Grip the wire with the
right hand, with the thumb
pointing along the
direction of the current.
The other fingers give the
direction of the magnetic
field around the wire.
How electric and magnetic fields interact:
• Michael Faraday developed the Law of
Induction, based on his discovery in 1831.
• He wrapped two insulated coils of wire
around an iron ring. He found that, upon
passing a current through one coil, a
momentary current was induced in the other
coil—mutual induction.
• If he moved a magnet through a loop of wire,
an electric current flowed in that wire. The
current also flowed if the loop was moved
over a stationary magnet.
Faraday’s Conclusion
• “The magnetic lines of force
and the wire must have a
motion relative to each
other to induce an electrical
current.”
• In other words, moving a
magnet through a coil of
wire will induce an electrical
current.
How to increase the strength of the
induced current (“Faraday’s Laws”)
1. Increase the strength of field
or the size of the magnet
2. Increase the speed of
motion
3. Change the angle (more
perpendicular)
4. Increase the number of turns
of coil
Electromagnetic Induction
• Moving a bar magnet
through a coil of wire
will induce a current
to flow through that
wire. NO SOURCE OF
ELECTRICITY NEEDED
– No batteries!
What are Electric Motors?
•An electric motor is a
device which
changes electrical
energy into
mechanical energy.
•Click the picture to
see how it works.
Electromagnets in Daily Life
• Electromagnets are common in everyday
appliances, and are becoming more
common as the need for technology
increases.
• Electromagnets are found in doorbells,
hard drives, speakers, MagLev trains, antishoplifting systems, MRI machines,
microphones, home security systems,
VCRs, tape decks, motors, and many
other everyday objects.
Junkyard cranes use electromagnets to
pick up large ferromagnetic material, like
scrap cars because they can turn the
magnet on and off as needed.
Let’s Review with Tim and Moby!
Closure
•Explain the relationship between electricity
and magnetism in an electromagnet.