MAGNETISM

Magnetism – a force to be reckoned with

Magnetism is the force that attracts and repels materials when all the electrons in the material flow in the same direction.

Nonmagnetic materials, such as plastic, glass and wood, have electrons that flow in different directions.

Making Magnets

Many metal objects can be magnetized rubbing them along a magnet in one direction.

Demagnetization may occur when these materials are heated or if the magnet is dropped or struck with a hard blow.

Magnetism

A magnetic pole is the area of a magnet where the magnetic effect is strongest. A tiny area of each magnet, called the domain, is magnetized due to the flow of electrons.

Attraction and repulsion

Like poles repel

and opposites

attract

Magnetic Fields

When a magnet touches a paper clip, the electrons in the paper clip begin to spin in the same direction as the electrons in the magnet, making the paper clip magnetic.

Once the paper clip is pulled outside the magnet's magnetic field, it loses its magnetism, and the electrons in the paper clip begin spinning in all sorts of different directions again.

Magnetic Fields

• A magnetic field is the region of magnetic force around a magnet.

• A magnetic domain is when all magnetic fields are lined up in the same way.

Magnets

Metals can be made into magnets by placing them in a strong magnetic fieldHowever they will lose magnetism quickly after being removed from the magnetic field.

A permanent magnet is a magnet made of a material that maintains magnetism, such as iron, nickel, and cobalt. Iron is the strongest.

More Magnetism

If you cut a magnet is cut in half, each piece retains its magnetic properties. This will happen no matter how many times you cut it since you are making a physical change.

Earth as a MagnetEarth has a magnetic field with two main poles. This magnetic field enables us to use compasses

Our planet's rotation causes molten iron-nickel in its outer core to circulate, creating electrical currents and a magnetic field (right). Think electromagnet on a planet size scale.

Electromagnets

Electromagnets are strong temporary magnets. A changing magnetic field causes current to flow in a conductor. Scientists call this property electromagnetic induction.It allows us to convert mechanical energy, a form of the kinetic energy of motion, into electricity.

Michael Faradayhttp://www.magnet.fsu.edu/education/tutorials/java/electromagneticinduction/index.htmlIn this interactive, replicate Faraday’s experiment to prove that electricity could be generated from magnetism, now known as electromagnetic induction

A magnetic field is in the same direction as the electric current.

Magnetism can be turned on and offYou can make an electromagnet by wrapping a wire around a piece of iron and sending a current through the wire with a battery.

Strength of

Electromagnets To increase the strength of an electromagnet:

Increase the voltage or currentIncrease the number of loops of wireMake the loops of wire tighterIncrease the amount of metal in the coreUse iron as the core

Classroom electromagnetvs. commercial electromagnet

Motors

Motors use electromagnetic

induction to convert electricity

into mechanical energy.

Generators

A generator is a motor opeating backwards. It converts mechanical energy into electricity. Most of the electrical energy we use comes from electric generators. The picture to the left shows an early model of a General Electric alternating current generator.

Transformers

• A transformer is a device that increases or decreases voltage.

• transformer – consists of two separate coils of insulated wire wrapped around an iron core

• step-up transformer – a transformer that increases voltage

• step-down transformer – a transformer that decreases voltage

Medical uses – the MRI• MRI scanners, like X-rays and CT scanners, take internal pictures by

generating three dimensional images in any orientation and at any depth in the body. Doctors can examine soft tissues like the spinal column and cord, identify multiple sclerosis, tumors, tendonitis, strokes and many other conditions. They produce better oictures than Xrays and CT scans but are also more costly.

Internet resources

http://www.albany.edu/~ms547669/enacmag.html Interactive pictured below. What will a magnet pick up?

http://www.magnet.fsu.edu/education/tutorials/timeline/Historical timelinehttp://www.fossweb.com/modules3-6/MagnetismandElectricity/Foss Webs interactives

Internet review games (easy)

http://www.quia.com/rr/245161.htmlMarta’s Magnets (elementary review, millionaire style)http://www.quia.com/cb/54471.htmlJeopardy style magnet and electricity

Internet review games (harder)

http://www.quia.com/quiz/2902523.htmlQuizhttp://www.quia.com/ba/174414.htmlBattleship style reviewhttp://www.quia.com/quiz/2407324.htmlQuiz based on Pearson chapters 1 & 3 electromagnets and magnetismhttp://www.quia.com/pop/89861.htmlUses of magnetism cloze activityhttp://www.quia.com/rr/95479.htmlMillionaire style review of electricity and magnetism

Compasses in Magnetic Fields

http://www.magnet.fsu.edu/education/tutorials/java/magcompass/index.htmlCompasses in Magnetic Fields

A tutorial that allows you to experiment with a compass to see how it responds to magnetic fields