ScienceScene



Introduction

Pollution: the introduction of harmful substances or products into the environment. According to a recent USA Today poll, ElectroPollution is the #1 environmental concern amongst Americans. The last ten years have seen an unprecedented increase in technologies (especially wireless telecommunications) and with it an exponential increase in ElectroPollution.

This handout was written for teachers interested in activities that would allow their students to experience the scientific basis of ElectroPollution. ElectroPollution is the addition of electromagnetic radiation to the environment through our use of anything that emits an electromagnetic field (EMF). A toaster used to make toast produces electromagnetic waves with a frequency of 60 Hertz. Cell phones produce microwave radiation in frequencies of 900 MHz and 1800 MHz range. All electronic gadgets, wired or battery operated, emit various electromagnetic frequencies into the environment. These electromagnetic frequencies interact with the naturally occurring electromagnetic field of humans, animals and the earth.

It is our purpose to investigate the fundamental concepts of electromagnetism that are the basis of ElectroPollution. These concepts are investigated through laboratory experiences designed to discover and apply them. It is our strong belief that true understanding, of a concept, is based upon direct observation and manipulation of the variables allowing one to observe the relationships in the concept. The following areas will be explored with activities designed to establish the scientific basis of ElectroPollution.

Magnets and Magnet Fields and their interaction

Flowing Electrons through a wire produce magnetic fields

A Magnet can cause electrons to flow in a wire

Interaction between magnetism and electricity

Magnets and Magnet Fields and their Interaction

Compass

A compass is a navigational instrument for determining direction relative to the earth's magnetic poles. It consists of a magnetized bar or needle turning freely upon a pivot (usually marked on the North end) free to align itself with Earth's magnetic field. The face of the compass generally highlights the cardinal points of north, south, east and west.

Suspended in Air

1. Hold String in hand with magnet hanging freely.

2. Twist magnet with other hand.

3. Repeat to determine if the magnet come to rest in the same position each time.

Compass Movement in Respect to a Magnet

1. While observing a compass, bring your magnet close to the compass.

2. Turn your magnet so the opposite end “pole” is pointing toward the compass and observe.

Magnetic Fields

Magnetic fields can be investigated using a directional compass which is nothing more than a magnetic needle mounted on a pivot so that it can move freely.

Using a battery and a conductor, electrons can be moved or caused to flow through the conductor. One can then investigate whether a magnetic field is present.

1. Place the compass flat on the table.

2. Place the battery parallel to the compass needle with the positive end of the battery pointing north. (see diagram)

3. Place the wire underneath the compass and observe the compass needle.

4. Touch the wire, to battery, only long enough to observe movement of the compass needle. (Be aware the wire will get hot)

5. Repeat with the wire on top of the compass. f the needle moves then there must be a magnetic field.

Flowing Electrons through a Wire Produce Magnetic Fields

Describing the Magnetic Field Associated With Flowing Electrons in a Wire

Keeping the battery oriented as illustrated. Half of the students should place the wire on top of the compass and the other half should place the wire underneath the compass. Touch the wire, to battery, only long enough to observe movement of the compass needle. (Be aware it will get hot)

Describing the Magnetic Field Around a Wire With Flowing Electrons

A magnetic field is a condition found in the region around an electric current, characterized by the existence of a detectable magnetic force at every point in the region and by the existence of magnetic poles.

Observing Magnetism Associated With Flowing Electrons

A battery can cause a current to flow through a wire which produces a magnetic field. This magnetic field can be used to pick up iron filings.

Making an Electromagnet

The magnetic field created by an electric current passing through a wire can be strengthened by wrapping wire around a piece of soft iron that becomes magnetized. The soft iron, of the paperclip, concentrates and strengthens the magnetic field when electric current flows through the wire. This arrangement is called an electromagnet. The iron core offers an easy path for the field inside the coil, and thus provides a minimum of magnetic resistance. Electromagnets allow magnetism to be turned on or off at will, and are currently used in many areas of modern society.

1. Take a nail and wrap it with wire.

2. Touch bare ends of wire to AA battery. (Be aware the wire will get hot)

3. Bring close to paperclip.

Batteries Can Light a Christmas tree Light bulb

1. Connect the Christmas light bulb to the battery.

2. Reverse the flow of the current by reversing the wires connected to the battery.

3. Observe any change.

Batteries Produce Flowing Electrons and Can Run a Motor

1. Connect the motor to a battery and observe.

2. Reverse the flow of the current by reversing the wires connected to the batteries and observe.

A Magnet Can Cause Electrons to Flow in a Wire

The MAP (Meaningful Applications of Physical Science) Generator

The MAP Generator uses the Faraday Principle of Electromagnetic Energy which states that if an electric conductor, like copper wire, is moved through a magnetic field, electric current will be generated and flow through the conductor. This simple generator is called an AC generator. This means that the voltage appearing at the two wires alternates between + and -, and - and + each time the magnet goes from one end to the other.

The Forever Flashlight

The Forever Flashlight also uses the Faraday Principle of Electromagnetic Energy to produce electric current to light a light. The Forever Flashlights use LED bulbs which are both bright and will not burn out. By shaking the Forever Flashlight back and forth for 15-30 seconds, enough electricity is generated to light the LED bulb for several minutes of continuous light.

Motors Can Produce Electricity and light a Christmas tree Light bulb

1. Connect the motor to a Christmas Light bulb.

2. Spin motor shaft and observe the Christmas Light bulb.

3. Observe any change.

Motors Can Produce Electricity and Light a Bi-colored LED

1. Connect the motor to a LED.

2. Spin motor shaft one way and observe the color the color of the LED.

3. Spin motor shaft the other way and observe the LED.

4. Observe and explain your results.

Motor Generator Demonstrator – A Summary (Magnetism & Electricity)

Motor

The electric motor is based on three principles. (1) Electric current passing through a conductor induces a magnetic field around the conductor. The coil, of a motor, is called an electromagnet because its magnetism is induced by electricity. (2) Like poles on a magnet repel each other, and unlike poles attract each other. (3) The direction of the current determines the polarity of an electromagnet.

The three parts of a direct-current motor are: (1) a stationary magnet, known as the field magnetic (2) a coil, called an armature that is free to rotate between the poles of a stationary magnet; (3) a device called a commutator, which changes the direction of the current in the armature. A current passes through the armature, making it an electromagnet. The armature turns until its poles are next to the opposite poles of the magnet. The armature would stop turning if the direction of the current on the armature were not reversed. The timing is such that the current reverses just as the N pole of the armature is next to the S pole of the magnet, The N pole of the armature becomes an S pole, and is repelled by the S pole of the magnet. The armature makes another half-turn, until its two poles are again next to the opposite poles on the magnet. Then the current reverses again, and the armature turns in the same direction for as long as the current remains on.

Generator

Associated with Oersted's discovery is the observation that moving a conductor in a strong magnetic field will cause electrons to move in the conductor, producing a current. A device used to produce electric current is called an electric generator. A simple electric generator would consist of a magnet and a coil of wire that could be spun in the magnetic field. If you rotate the coil of wire between the poles of the magnet electricity will be produced in the coil.

Interaction Between Magnetism and Electricity

Making a HomoPolar Motor

Simple electric motors were first invented in 1821 by the ninetieth century English scientist Michael Faraday. He built a type of electric motor which is referred to as a homopolar motor. In essences such a motor consists of a conducting disc in the neighborhood of a permanent magnet that is free to rotate. A source of direct current is then allowed to pass through two arbitrary points on the disc maintaining continuous rotation. A homopolar motor is able to produce continuous rotation with the same electric polarity for its operation. The Greek equivalent of same is homo which gives us the name homopolar.

The cheap and ready availability of very strong permanent magnets in the form of rare-earth magnets; has lead to renewed interest in the design and construction of new forms of ever simpler homopolar motors. Replacement of the conducting disc used in a homopolar motor with a conducting disc which produces a magnetic field of its own allows for a simplification in the design of a homopolar motor.

In the dangling homopolar motor, one side of a small neodymium disc magnet is stuck to the level head of a ferromagnetic screw. The screw, in turn, becomes magnetized owing to the strength of the neodymium magnet. The pointy end of the screw can now be stuck to the bottom terminal of a battery where it hangs freely under gravity since the battery's casing is ferromagnetic and provides a very low friction connection between the hanging magnet and the battery. If one end of a copper wire is pressed against the top terminal of the battery using your finger, brushing the other end of the wire against the rim of the disc magnet completes the circuit, causes current to flow and leads to the spinning of the disc.

The HomoPolar Motor Explained

So what causes the disc to rotate? Upon brushing the wire up against the rim of the magnet, current flows over its chrome-plated surface to the central connection point at the head of the attached screw. As the magnet itself now takes on a current carrying function, a Lorentz force acts tangentially to the inwardly allowing current in accordance with the right-hand rule. Hence a resultant torque acts on the disc about the axle formed by the attached screw and causes the disc to spin

The direction of current flow is indicated by the purple arrows. The magnetic field lines are illustrated in blue. The flow of electricity through the magnet produces a magnetic field which creates a force perpendicular to this flow. This force, indicated by the green arrow, causes the magnet to spin.

Applications: Demonstration that create ElectroPollution

Homemade Speaker

A speaker takes the electrical signal and translates it into physical vibrations to create sound waves. A common speaker contains a coil and a permanent magnet. When electrical impulses pass through the coil of a speaker, it interacts with the permanent magnet and moves back and forth. A rapid succession of varying impulses, such as a radio sends to its speaker, will cause the coil to vibrate producing faint sounds.

You will need a battery powered radio with a single earphone jack. Wrap number 22 – 28 coated copper wire around a small cup to produce a coil of approximately 50 turns. Cut the earphone from its cord. Separate the 2 wires that make up the cord, for a distance of a few centimeters. Carefully remove about 2 cm of the insulation from the end of each wire. Tightly connect the wires to a coil of wire. Attach this coil to the bottom of a large plastic cup with white glue. Turn on the radio end tune it to a clear station. Plug the earphone cord (now corrected to the coil) into the radio. Turn up to volume, on the radio, and bring a strong neodymium magnet close to the coil to hear the speaker. Explain this application by using what you have learned about electromagnetism.

Musical Motor

A miniature electric motor and a common speaker, have the same basic components: a coil and a permanent magnet. When electrical impulses pass through the voice coil of a speaker, it interacts with the permanent magnet and moves back and forth.

What will happen if electrical impulses are passed through the armature of a motor? Each pulse, depending upon its intensity and duration, will cause a very sight movement of the armature. A rapid succession of varying impulses, such as a radio sends to its speaker, will cause the armature to vibrate. These vibrations produce faint sounds.

You will need a battery powered radio with a single earphone that can be plugged into it. Cut the earphone from its cord. Separate the 2 wires that make up the cord for a distance of a few centimeters. Carefully remove about 2 cm of the insulation from the end of each wire. Tightly connect the wires to a miniature electric motor. It is best to use a motor that will operate on as little as 1.5 volts. Try several motors as some work better than others.

Turn on the radio end tune it to a clear station. Plug the earphone cord (now corrected to the motor) into the radio. Turn up to volume you will probably feel the motor vibrating. If you hold it close to your ear, you should be able to her the radio station. You can amplify the sound by pressing the motor against the bottom of plastic cup to amplify the sound. Explain this application by using what you have learned about electromagnetism.

Modulated Coil

Using an electromagnet, wirelessly transfer the sound from a radio to the speaker of a tape player.

Materials

wire stripper, about 3 ft (1 m) of insulated wire #22 solid insulated copper wire, steel bolt (about 1/4-in diameter and 2 in long), audio cable, 6 ft (2 m), 1/8- in phone plug on one, small radio with headphone jack, portable tape cassette player with speaker

Procedure

1. Use a wire stripper to remove about half an inch (1.2 cm) of the insulation from each end of the wire.

2. Wrap the wire around the bolt, leaving about an inch (2.5 cm) of wire free on the starting end of the wire. Wrap the wire around the bolt, building up multiple layers until you have at least 20 wraps.

3. Attach the audio cable to the ends of the wire on the bolt.

4. Turn on the radio and find a radio station with a strong, clear signal. Adjust the volume to medium-high. Plug the phone plug on the audio cable into the headphone jack on the radio. You will no longer hear the radio, since the signal is being fed to the headphone circuit instead of to the speaker.

5. Using a tape player, without a tape, press the play button. Adjust the volume control on the tape player to medium-high. Since there is no tape in the player, you should not hear any significant sound.

6. Bring the wire-wrapped bolt near the head of the tape player. You should hear the sound from the radio station playing through the speaker of the tape player.

The radio sends an electric current through the audio cable and through the coils of wire wrapped around the bolt. The wire-wrapped bolt becomes an electromagnet, with the strength of its magnetic field determined by the size of the current flowing through the coil. The current varies in strength, due to the audio, causing the magnetic field of the electromagnet to also vary. The head of the tape player is essentially a device for detecting very small variations in a magnetic field. Normally it detects variations in the magnetic field on the audiotape as the tape travels by. In this case, however, it senses the fluctuating magnetic field in the coils of wire wrapped around the bolt.

In principle you could use the coil of wire alone, without the bolt. You would then have an electromagnet with an air core rather than an iron core. The iron core, however, greatly intensifies the magnetic field. What would you have to do to achieve the same effect with an air core? Check your reasoning by building an air-coil.

Transmitting Electromagnetic Waves

You will need a battery powered radio with an earphone jack that can be plugged into and two coils of wire. Make one coil by wrapping number 22 – 28 coated copper wire around a round object approximately 8 cm. to produce a coil of approximately 75 turns.

Make the second coil by wrapping number 22 – 28 coated copper wire around a round object approximately 12 cm. to produce a coil of approximately 50 turns. Cut two earphones from their cord. Separate the 2 wires that make up the cord tor a distance of a few centimeters. Remove about 2 cm of the insulation from the end of each wire. Connect the wires to the wires from the coil. Be sure that you have tight connection.

Now that you have the coils connect them as illustrated to the radio and amplifier. By changing the distance between the coils you should be able to hear a difference in loudness of the sound being played by the radio. Explain this application by using what you have learned about electromagnetism.

Final Thoughts Concerning ElectroPollution

In this fascinating, changing and ever controversial world we live and teach in, there arises many issues. One of these issues is the concept of pollution. According to the dictionary pollution occurs when there is an introduction of harmful substances or products into the environment. When pollution exists we have an environmental problem.

A definition is a good start but we must also recognize that all environmental problems have three components Social/Political, Economic and Scientific. Strong positions and answers for environmental problems can come from any one of these component areas. When you select an answer to an environmental problem it represents a point of view that can be used to address the problem.

The purpose of this workshop was to provide demonstrations and activities selected to establish the fundamental scientific basis of ElectroPollution. This fundamental understanding will allow us to base our answers on facts not opinion, beliefs or popular culture. When your answers are based on fundamental science you have the assurance that your answer has a high probability of being correct.

Although the debate continues the medical effects of ElectroPollution lack adequate foundation and have yet to be confirmed. Many physicists argue that there is no plausible mechanism by which low levels of non-ionizing radiation could affect living tissue, as magnetic fields are thought to be harmless, and electric fields are thought to flow around, rather than through the human body.

Materials:

Magnets: CMS Magnetics, Inc, P.O. Box 941122, Plano, TX, 75094, 866-342-1300,

Part Number “N42, 1/2"X1/4". Axially Magnetized, SKU: ND038-42NM”

Motors: Kelvin, 280 Adams Blvd, Farmingdale, NY, 11735, 800-535-8469

Wire: Arbor Scientific- P.O. Box 2750, Ann Arbor, MI, 48106-2750

Phone 1-800-367-6695, Fax 1-734-913-6201

Kelvin, 280 Adams Blvd, Farmingdale, NY, 11735, 800-535-8469

28 Ga. Magnet Wire, 1 lb. Spool, Code: 330134

Compass: Discount Science Supply, 28475 Greenfield Road, Southfields, MI 48076

Phone 1-800-938-4459

References:

1. A Simple Rolling Homopolar Motor, Seán M. Stewart, 6 August 2006; revised 8 august 2006

2. Physics is FUNdamental, Michael H. Suckley, 2008

3. Practical Activities for Strengthening Your Teaching of Physical Science Concepts, Al Guenther, 2000

Workshop Presenters:

The presenters are educators with approximately 100 years of exemplary science teaching between them at grade levels from third grade through college. They have worked together for over fifteen years to encourage and promote physics education in the elementary and middle schools in the Midwest. The goals of the workshops are to:

• Enhance upper elementary and middle school teacher's understanding of physics concepts.

• Provide teachers with hands-on heads-on activities for effectively teaching these concepts to their students.

Dr. Michael Suckley has over 40 years of teaching and consulting experience at middle, high school and college level. He is Professor emeritus Macomb Community College for Physical and Environmental Science and has authored two physical science textbooks.

Mr. Paul A. Klozik has over 36 years of teaching experience at the high school level and Community College. Developed and presented workshops for science teachers for Warren Consolidated Schools. Introduced and promoted Science Olympics and headed the Steering Committee for district science curriculum.

Each of these educators has an intense desire to help in the improvement of science education. If you would like to learn more about the presentations or you would like the team to develop a customized workshop for your teachers and visit your school district please contact us.

Email MAP@

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Dr. M. H. Suckley & Mr. P. A. Klozik

Email: MAP@

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Coil of Wire

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Coil of Wire

Magnet

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