As freshly laundered clothes tumble about in a hot dryer, they rub against one another. Sliding friction transfers electric charges from one piece of clothing to the other so that some items become positively charged and others negatively charged. These charge accumulations produce static cling. Fabric softener is a soap-like chemical that binds to wet fabric fibers and lubricates them. This lubrication is what softens the clothes. But fabric softener also attracts moisture, which in turn reduces static cling.
1. As you unload the dryer you find several socks clinging to a shirt. How do the charges on the socks and shirt compare to one another?
2. As you pull the socks off the shirt, you do work on the socks. What form is your energy being transformed into?
3. Suppose that your socks are covered with positive charge. As you pull them away from the shirt, what happens to the voltage of the charges on the socks?
4. The farther each sock is from the shirt, the less that sock and shirt attract one another. Explain.
5. After removing them from the shirt, you find that the socks repel one another. Explain.
6. If you put one of the clean socks on the wall, it sticks. The wall is made of an insulating material that was not initially charged, so why does the charged sock stick to it?
7. If you hold a metal needle so that its point is very close to the charged sock, a faint blue glow will appear at the needle's tip and the sock will lose some of its charge. What is happening at the needle's tip that is reducing the charge on the sock?
8. The next time you do your clothes you decide to add fabric softener. Your clothes emerge from the dryer with a thin layer of moisture on them and this moisture permits charge to move freely about the clothes. Why does this charge mobility prevent the build-up of separated charge?