Magnetism From Electricity

What electromagnets are and how they are important to our daily

lives.

What is a Maglev Train?• A train with no wheels • Floats on a cushion of

air• Suspended by same-

poled magnetic fields generated by a series of electro-magnets through the rail & the train

Who is responsible for the discovery of Electromagnetism?

• Hans Christian Oersted• Found that a compass

was affected by a nearby electrified wire

• The compass needle moved differently depending on which direction the electricity flowed

What is Electromagnetism?

• The interaction between magnets and electricity

• Are useful for a large number of applications

• Can be controlled and manipulated

….more on electromagnetism.• By itself, the magnetic

field caused by electricity, is actually not strong enough to be very useful

• However electromagnets and solenoids can strengthen the magnetic field

What is a Solenoid?• A coil of wire that

produces a magnetic field when electric current passes through it

• The more loops = the stronger the magnetic field

• The magnetic field is very similar to a bar magnet’s magnetic field

Also the magnetic field increases with

increased current

What is an Electromagnet?• Made up of a solenoid

wrapped around an iron core

• The magnetic field (MF) aligns the domains in the iron core

• The MF is the combined MF of the coil and iron core

Can electromagnets be made stronger?

• Yes, by increasing the number of loops per meter (or per

centimeter) in the solenoid– Increasing the

number of loops around the iron core

• Remember Maglev trains?

Can electromagnets be turned off and on?

• Think about the practical applications of being able to start & stop magnetism

• A junk yard uses a huge electromagnet to pick up & drop tons of material!

What are some other practical uses of electromagnets?

• Doorbells • Electric locks• Circuit breakers• MRI machines

– Magnetic Resonance Imaging

• Speakers of any size• And many more

What is the relationship between magnetic force & electric current?

• If a current-carrying wire can cause a magnet to move…

• Then a magnet can cause a current-carrying wire to move

• This property is important in how electric motors work

What are electric motors?• A device that changes electrical energy into

mechanical energy• All electric motors have ….

– Armature - a loop or coil of wire that rotates– Armature is mounted between the poles of a permanent

magnet & electromagnet• Can use Direct Current (DC) - electricity moving in

one direction• Can use Alternating Current (AC) - electricity

moving in two directions

A Direct Current (DC) Electric Motor

A Direct Current (DC) Electric Motorcont…

What is a Galvanometer?

• Measures current• Can detect direction

of current • Useful in detecting

electrical polarity• Electricians use

instruments like this daily

Be sure to check the wikispace for more

information, a copy of this PowerPoint & website’s that

show details of electric motorshttps://nemsgoldeneagles.wikispaces.com/