Lesson Plan 2
Opposites Attracting

Objectives

• Demonstrate how electrical charges attract and repel.
• Draw conclusions about the nature of electricity.

Materials

• Cheerios or other cereal shaped as rings
• wire clothes hanger
• plastic comb
• piece of wool
• foam cup
• large nail (at least one inch longer than width of cup)

Subject

• science

Students may find it incredible that there is a connection between lightning—which can be as hot as 50,000 degrees Fahrenheit—and the static electricity in this experiment, which produces not so much as a snap, crackle, or pop.

Procedure
1. Cut two triangular notches out of the rim of the cup, on opposite sides, so that they will form a cradle for the nail.
2. Bend the ends of the coat hanger together until it can stand upright. Twist the hook of the hanger in the opposite direction and uncurl it a bit. (The contraption will resemble a swan.)
3. Cut off a few inches of thread. Tie a knot around the Cheerio and tie the other end of the thread to the hook (the beak of the swan).
4. Make adjustments so that the Cheerio hangs within half an inch of the nail point. Make sure the Cheerio has room to swing freely.
5. Vigorously rub the comb with the wool.
6. Touch the head of the nail with the comb. The Cheerio, at the other end, should touch the point of the nail and then jump back.
7. Rub the comb again and repeat the experiment. This time, the Cheerio should swing out, away from the nail.
8. Ask students to draw conclusions based on the previous action of the Cheerio.

We use the term charged to describe bodies in which the numbers of protons and electrons are unequal. We use Franklin’s terms positive and negative to describe the charges. If there are more protons than electrons, the charge is positive; if there are more electrons, it is negative. Unlike charges attract. When the bodies carrying them touch, there is a transfer of electrons in which the two charges tend to equalize each other.

When we rub the comb, it picks up electrons from the wool and becomes negatively charged. The charge attracts the Cheerio by way of the nail, which acts as a conductor. But when the Cheerio touches the nail, it takes on the negative charge. Like charges repel. The next time we do the experiment, the Cheerio continues to be repelled.

Lightning, too, is a matter of positive and negative charges. In the turbulence of a storm cloud, a negative charge builds in the bottom of the cloud. It induces positive charges on the ground and within the clouds. At the swift meeting of positive and negative, we see the flash.

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