Magnetism Magnetic field Magnetic pole North South Repel Attract Lodestone	Magnetic induction Temporary magnet Permanent magnet Magnetosphere Aurora Left-hand Rule Electromagnet Electric motor	Commutator Electromagnetic induction generator Transformer Step-up Step-down Primary coil Secondary coil

Magnetic field:

Area around a magnet where magnetic forces act.
A compass is used to detect the Earth's magnetic field.

Magnetic poles:

The concentration of force at the end of a magnet.
• One end of a magnet points North.
• One end of a magnet points South.
• New poles will form when a magnet is broken in half.
• Like poles repel each other.
• Unlike poles attract each other.

Semiconductor Processor

The first magnets were pieces of the naturally occuring ore magnetite, or "lodestone". It was learned that lodestone could be used to turn iron objects into "artificial" magnets by stroking them in the same direction several times. Until 1821, this was the only kind of magnetism known.

Magnetic induction: the process by which a material is made into a magnet.

During this process, atoms in a substance are aligned.

Temporary magnets:
Materials that are easy to magnetize, and loose their magnetism quickly.
Permanent magnets:
Materials that are hard to magnetize, but tend to stay magnetized.

Earth's magnetism:

Magnetosphere: the region of the earth's magnetic field.
• Extends beyond the atmosphere.
• Composed of charged particles given off by the sun.
• The collision of these particles in the upper atmosphere causes the Aurora.

With your table, ask your teacher for materials to map the lines of magnetic force around a bar magnet. When you have the material set up to show these lines of force, use the class camera to take a digital picture of the arrangement. Save this picture on your computer.

Test Your Concept Understanding: Why does a bar magnet looses its magnetism when repeatedly struck with a hammer. Read about the Earth's magnetic north pole. The magnetic north pole of the Earth is moving. How far does this magnetic pole move in one year? The pole does not move in a straight line. Describe the shape of its motion. Learn about the magnetosphere. When was the compass discovered? How a compass worked was not described until 1600. Who did it and what was his explaination? Read about the polar aurora. Who first used the term "aurora borealis", and in what year? How far above the Earth's surface does the aurora borealis form?

Day 3 - 4

Why can't A.C. electricity be used to make an electromagnet?

In 1821, a Danish scientist, Hans Christian Oersted, noticed that an electric current flowing through a wire caused a nearby compass needle to move. Further studies by Oersted led him to conclude that any wire carrying an electric current has a magnetic field around it.

In France, Andre-Marie Ampere studied Oersted's observations and concluded that the nature of magnetism was quite different from what everyone had believed. It was basically a force between electric currents. Two parallel currents moving in the same direction produced a force of attraction while currents moving in oposite directions produced a repelling force.

The First Left-hand Rule:

"When a current-carrying wire is grasped in the left hand, the thumb pointing in the direction of the electron current, from negative (-) to positive (+), the fingers will point in the direction of the magnetic induction field."

Electromagnet:

Produced by a current running through a coil of wire.

• The strength of an electromagnet is increased by wrapped the coil around an iron core.
• The magnetic field is active only when the current is flowing.
• The more coils of wire, the stronger magnet.
• The polarity of an electromagnet is found using The Second Left-hand Rule:

Electric motor:

Converts electrical energy into mechanical energy.

• An electric motor consists of:
  • A electromagnet free to rotate on a shaft.
  • A fixed permanent magnet.
  • The alternating current running through the electromagnet causes the poles to keep switching. First a push, then a pull within the field of the permanent magnet causes the electromagnet to spin.
  • Commutator - used to rotate the electromagnet poles when a motor is powered by DC electricity.

Generators convert mechanical energy onto electrical energy.

• A generator consists of:
  • A coil of wire that rotates in a magnetic field.
  • A permanent magnet surrounding the turning wire.
  • When the turning wire goes through one side of the field, a current is induced.
  • As the wire goes through the other side of the field, the current flows in the opposite direction.
  • Generators produce alternating current.
  • Batteries produce direct current.

• A transformer consists of:
  • Two coils of insulated wire wrapped around the same iron core
  • Primary coil - an electric current is passed through this coil.
  • Secondary coil - an electric current is induced in this coil.
  • The coil with the most turns of wire will have the most current.
    
    • Step-up transformer - one that increases the current.
    • Step-down transformer - one that decreases the current.
  Use the website to experiment with a transformer

   

  Any volunteers may have extra class time to build a working model of an electric motor from plans found on the World Wide Web. Find directions you can use to make an electric motor with simple materials. Make a diagram of this motor. If you find a diagram on the Web, you can print that. Gather the materials needed. Your science teacher will not furnish any materials. Build a working model of this electric motor.

   

  Test Your Concept Understanding: Look at the drawing of the transformer above to answer this question. Which side (left or right) would be the primary coil if this were a step-down transformer? Explain why electromagnets cannot be made using alternating electric current. There are many types of commercial magnets. What is an Alnico magnet? What is the most powerful class of magnet material commercially available today? What is a ceramic magnet made of?

Research Links:

• Magnetism - NASA, International Solar-Terrestrial Physics
• Earth's Magnetic Field - Canadian National Geomagnetism Program
• Commercial Magnets - SG Magnets
• Magnets - University of Michigan
• Magnetics - Colorado School of Mines
• How Motors Work - Micro Mo Electronics
• Motors - Bizarre Stuff
• Stripped Down Motor - The Exploratorium
• Elementary Motor - The Internet Science Room
• Experimental Space Plasma Group - University of New Hampshire

Physical Science

The northern lights are caused by the collision of charged particles in the upper atmosphere.

A.C. electricity keeps changing its direction of flow. This keeps poles and a magnetic field from forming.