Chapter 12 Lesson 4, "Relationship Between Electricity and Magnetism"

Materials:

• Worksheet, 12-04 "Relationship Between Electricity and Magnetism"

Objective:

• Students will Explain how magnetism and electricity are related.
• Students will describe electromagnetism
• Students will list devices that use electromagnetism
• Students will explain how magnetism can be produced from electricity.

Anticipatory Set:* Magnets are fun to play with but do they really play an important role in our lives? Show the students several devises that depend on magnetism to work. Telephone, door bell. Automobile, Stereo, Loudspeaker, tape recorder, and snow machine.

Teacher Input:* In order to understand how magnetism can be controlled so that it can be used in all those things we have to start by looking at how electricity affects magnetism Here you see a diagram of a open circuit. The wire is wrapped around an iron nail. Next to the nail is a compass on both ends. The compass is measuring the magnetic field. If we close the circuit look what the compass does. If we place the compass in the middle of the wire it will move like this. This is what is happening. As electricity begins to flow around this nail it creates a magnetic field around the nail. From looking at how the compasses reacted we see that the field extends outward at the ends of the nail so those are the north and south poles then the field circles the center of the nail. In the investigation tomorrow you will get to set this up. You will then use iron filing to see if you can get a pattern like this. So to sum this up. If we run a current around an iron center we can end up with a magnetic field of influence just like a bar magnet has or the entire earth as far as that goes. Now, how can we use this idea in real world applications. You have all probably seen a crane like this in Fairbanks or a movie. The operator can turn on a switch which send electrical current around the iron disc. Then when he wants to drop the load he can hit the switch off. Have you ever seen a train like this one. This is a train made by college students who were trying to create cheaper ways of travel. This train and ones like it use magnetic field to lift the train off the tracks. The field then can be altered to make the train move. This allows for almost do friction and the fastest trains in the world. On page 362 you'll find a picture of how a speaker works. The electric signal turns magnets on and off with in turn move a vibrating plate and create the sound. By using magnetic like this we can do all sorts of things. In this electric guitar the vibrating string causes a fluctuating magnetic field which then sends a fluctuating electric signal to a speaker which turns it back into magnetic fields and amplifies the sound. A simple thing like a doorbell the magnetic field pulses causing the hammer to vibrate back and fourth against the bell. These are all pretty simple devises that use magnetism to push or pull. We can also use that magnetism to cause a rotary motion. In a motor, the current alternates causing the north and south pole in the magnet to switch back and forth. We see the motor in thousands of different devises. Here is a diagram of a the motor in a CD player. The batteries changes the magnetic field at the bottom and cause the rotation of the axial that the CD sits on. Have the students list as many things as they can that have a motor in them. (Point out that an engine is different. It does not use electricity for power.

Other than the train and crane, up until now we have talked about fairly small, weak magnets. The scientific study of magnets has made great advancement in the last 20-30 years. Scientists have been able to create super conducting magnets. These can produce magnetic fields 200,000 times greater than the earth's. They are made out of materials with very little resistance and have really helped us utilize the power of magnetism. Here this super magnet has been able to use its power on a very small level. This machine utilizes very powerful magnetic fields to analyze molecules. This has helped in the development of new and better drugs. The MRI we talked about the other day uses a very powerful magnetic field to take pictures of the inside of the human body. They even have whole body MRI's now that can take pictures of the entire body and once and you don't have to be cramped in a little space. Powerful magnets like this one can even be used in cancer the ropy.This machine uses a very powerful magnetic field to speed up atoms. It works like a sling shot to shoot one atom at another nearly as fast as the spread of light. This has enables us to break apart or build new bigger atoms. Theoretically we could use this to turn lead into gold. If you have friends in Fairbanks chances are they have cell phones. Cell phones are just another of thousands of devises that use magnetic fields for communications as well.

Guided Practice:* Students will work in pairs or groups to answer the questions on page 366

Independent Practice:* Students will read Lesson 4, "Relationship Between Electricity and Magnetism" then complete the worksheet, 12-04 "Relationship Between Electricity and Magnetism".

Check for Understanding:* Students will take the quiz 12-04 "Relationship Between Electricity and Magnetism"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-1 Students will understand models describing the nature of molecules, atoms, and sub-atomic particles and the relation of the models to the structure and behavior of matter (Structure of Matter);
• SCI A-2 Students will understand the physical, chemical, and nuclear changes and interactions that result in observable changes in the properties of matter (Changes and Interactions of Matter);
• SCI A-5 Students will understand the strength and effects of forces of nature, including gravity and electromagnetic radiation (Forces of Nature);
• SCI A-8 Students will understand the scientific principles and models that
  describe the nature of physical, chemical, and nuclear reactions;
  state that whenever energy is reduced in one place, it is increased somewhere else by the same amount; and
  state that whenever there is a transformation of energy, some energy is spent in ways that make it unavailable for use (Energy Transformations);
• SCI A-9 Students will understand the transfers and transformations of matter and energy that link living things and their physical
• SCI A-15 Students will use science to understand and describe the local environment (Local Knowledge); and: