New Page 3

AIMS:

1. What is an electromagnet?

2. What is static electricity?

3. How are electricity and magnetism related?

MOTIVATION:

Ask students if they know how they can make an on and off magnet.

Explain to them that we can make a magnet by using electricity! This is one of the ways that magnetism and electricity are related.

PROCEDURE:

1. Have the students log on to http://science.howstuffworks.com/electromagnet2.htm to find out what an electromagnet is and how it works.

2. Ask students to fill in the database using the material from the website. For a blank database, click here.

QUESTION

ANSWER

1. In which direction do electrons flow in a battery?

Electrons will flow from the negative side of the battery to the positive side as fast as they can.

2. What three things happen if you connect a wire from the negative to the positive ends of a battery terminal?

Electrons will flow from the negative side of the battery to the positive side as fast as they can.
The battery will drain fairly quickly (in a matter of several minutes).
A small magnetic field is generated in the wire.

3.How can you see the magnetic field formed around wires containing electricity?

Put the compass on the table and, with the wire near the compass, connect the wire between the positive and negative ends of the battery for a few seconds. What you will notice is that the compass needle swings.

Initially, the compass will be pointing toward the Earth's north pole (whatever direction that is for you), as shown in the figure on the right. When you connect the wire to the battery, the compass needle swings because the needle is itself a small magnet with a north and south end. Being small, it is sensitive to small magnetic fields. Therefore, the compass is affected by the magnetic field created in the wire by the flow of electrons.

4.Does a magnetic field weaken or strengthen as you move away from the electromagnet?

The field weakens as you move away from the wire (so the lines are farther apart as they get farther from the wire).

5.How can we increase the size of the magnetic field?

An easy way to amplify the wire's magnetic field is to coil the wire, as shown below:

One loop's magnetic field

For example, if you wrap your wire around a nail 10 times, connect the wire to the battery and bring one end of the nail near the compass, you will find that it has a much larger effect on the compass.

Lab Activity:

ELECTROMAGNET

This activity is taken from Janice VanCleave Physics for Every Kid, John Wiley and Sons, 1991

(See my student samples here)

Problem: How can we show that an electric current produces a magnetic field?

Hypothesis: We think if we wrap a wire tightly around a nail and attach each end to opposite terminals on a battery, then we can show that a magnetic field is formed.

Materials: 1 yard of wire, battery, long iron nail, paper clips

Procedure: 1. Wrap the wire tightly around the nail, leaving about 3 inches of free wire on each end. 2. Strip the insulation off both ends of the wire. 3. Secure one end of the wire to one pole of the battery. 4. Touch the free end of the wire to the other battery pole while touching the nail to a pile of paper clips. 5. Lift the nail while keeping the ends of the wire on the battery poles. 6. When the nail starts to feel warm, disconnect the wire end you are holding against the battery pole.

Observations: The paper clips stick to the iron nail when the wires are connected to both battery poles.

Conclusion: There is an electric field around all wires carrying an electric current. Straight wires have a weak magnetic filed around them. The strength of the magnetic field around the wore was increased by coiling the wire into a smaller space, placing a magnetic material-the nail- inside the could of wire, and increasing the electrical flow through the wire- attaching a battery. The iron nail became magnetized and attracted the paper clips.

3. Ask students if they have ever received a shock when they went to turn on a light or touch a doorknob?

Does anyone know why that happens? Lead students into a discussion on static electricity. Have them review what static electricity is from their vocabulary words. In order for children to understand what static electricity is, they have to understand the nature of atoms. Let them log on to http://sciencemadesimple.com/static.html to answer the following questions on the database. For a blank student version, click here.

QUESTION	ANSWER
1. What are the three particles atoms are made of?	In the middle of each atom is a "nucleus." The nucleus contains two kinds of tiny particles, called protons and neutrons. Orbiting around the nucleus are even smaller particles called electrons.
2. What charge does each particle have?	Protons have what we call a "positive" (+) charge. Electrons have a "negative" (-) charge. Neutrons have no charge, they are neutral.
3. What is a charged atom called?	A charged atom is called an "ion."
4. Why are some materials considered insulators?	Some materials hold their electrons very tightly. Electrons do not move through them very well. These things are called insulators.
5. Why are some materials considered conductors?	Other materials have some loosely held electrons, which move through them very easily. These are called conductors.
6. How can we make static electricity?	One very common way is to rub two objects together. If they are made of different materials, and are both insulators, electrons may be transferred (or moved) from one to the other
7. How do positive and negative charges behave?	Now, positive and negative charges behave in interesting ways. Did you ever hear the saying that opposites attract? Well, it's true. Two things with opposite, or different charges (a positive and a negative) will attract, or pull towards each other. Things with the same charge (two positives or two negatives) will repel, or push away from each other.
8. Why don't we feel static electricity in the summer like we do in the winter?	We usually only notice static electricity in the winter when the air is very dry. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you can not build up as big a charge.

4. Have students choose one of the following activities to show static electricity: You can click here for blank student versions.

LAB ACTIVITY 1:

STREAMERS

This activity is taken from Janice VanCleave Physics for Every Kid, John Wiley and Sons, 1991

Problem: How can we charge an object with static electricity?

Hypothesis: We think if _____________________________

_________________________________________then________

____________________________________________________.

Materials: comb, tissue paper, scissors, and ruler

Procedure: 1. Cut a strip of tissue paper about 3" by 10" 2. Cut long, thin strips in the paper, leaving one end uncut. 3. Quickly move the comb through your clean, dry, oil-free hair. 4. Hold the teeth of the comb near, but not touching, the cut end of the paper strips.

Observations: The thin paper strips move toward the comb.

Conclusion: We learned that we could rub electrons off our hair onto the comb. We created opposite charges on the comb and our hair. Opposite charges repel each other. This is strong enough to make the strips of paper move toward the comb.

LAB ACTIVITY 2:

TINKLE

This activity is taken from Janice VanCleave Physics for Every Kid, John Wiley and Sons, 1991

Problem: How can we demonstrate the effect of static electricity?

Hypothesis: We think if ____________________________

_______________________________________________then

___________________________________________________.

Materials: comb, aluminum foil, scissors

Procedure: 1. Cut ten tiny pieces of aluminum foil and lay them on a table. 2. Quickly move the comb through clean, dry, oil-free hair. 3. Hold the teeth of the comb above the foil pieces. Do not touch the aluminum.

Observations/Results: We saw the aluminum foil pieces move toward the comb. The metal actually moves through the air to reach the comb.

Conclusion: The comb rubs electrons off your hair and becomes negatively charged. As the comb approaches the metal pieces, the negative electrons in the metal moves away from the comb, leaving more positive charges on the surface of the metal. Like charges repel each other and unlike charges attract. The attraction of between the negatively charged comb and the positive area on the metal is strong enough to overcome the downward pull of gravity, and the metal pieces move through the air to stick to the comb.