From the previous experiment, we made negative charges transfer onto a balloon when it was rubbed with wool. Because the balloon now has more negative charges than positive charges, it has a net negative charge. This type of “charging” is called contact charging.
Contact charging can also produce objects with a positive charge. For an object to become positive, it must lose some of its negative charges. This loss offsets the neutral balance to produce a net positive charge.
Things Required:
10-inch strip of nylon fabric
A pair of scissors
Plastic grocery bag
Directions:
Use your scissors to cut a 10-inch strip of nylon. Firmly hold the middle of the strip, allowing the halves to hang downward. Grasp the nylon with the plastic bag. Stroke both halves of the fabric several times. What happens when you stop stroking the nylon? What causes the nylon to behave this way?
This Is What Happens:
Unlike wool, your plastic does not easily give up its negative charges. On the contrary, it has a tendency to take in negative charges. When the plastic rubbed along the nylon, negative charges transferred to the plastic material. This left the nylon strips with a positive charge. Since both hanging halves had the same charge, they repelled each other, causing the free ends to separate.
