When you rub a balloon on a woolen sweater, you can charge it: the sweater and the balloon will charge up, one with a negative charge, the other with a postive charge. The same happens with clouds or when you walk on a carpet on a dry winter's day. Such a charge is called static electricity.

When this happens, you can move your hand close to some object or person and cause a spark to fly between you and them. Like charges repell, unlike attract. If you move your postively (+) charged hand (or nose) near something or someone else, the side near you becomes negatively charged (more electrons move into the space near you). If you are close enough to an object, a spark may fly between you and the object. The more pointy the object you are close to, the more force there is to cause the charge to jump from one object to the other. That is why tree tops get hit by lightning. (Ed. note: if you are interested in lightning, check out this link: The Lightning Page).

When part of a person or inanimate object becomes charged, and it is connected to the ground, it will become neutral: either the surplus electrons will go to the ground, or more electrons will flow into you from the ground. A small charge is not too painful, but a lot of charge moving through the body can hurt and kill.

Even small sparks can be a nuisance. I once tried to turn on my TV in the winter, on a dry day, and the spark that jumped between me and the TV control button fried the control board inside the TV! It cost $140.00 to get a new one!

Your body makes electricity of its own and uses it for many things: the way muscles contract involves electric charges moving from outside the cells of the muscles into the inside. The same happens when messages travel along nerves. The charge moves into the nerve cell. Our hearts are regulated by small pulses; like clocks they "tell" the heart muscle when to pump. Electric shocks can hurt or help: a sudden surge of electric charge from outside can confuse the heart and kill, but doctors know how to restore a heart that has stopped with an electric charge. Doctors also install pacemakers that help people whose electric "clocks" in the heart do not work well.

You may have seen the experiment that uses a Van de Graaf: a charging machine that charges a large metal ball. One way to show it is to show sparks flying from the big ball to a smaller ball that is connected to the ground. Another way involves a person insulated from the ground, perferably with loose hair. He or she puts one hand on the ball, and gets charged with it. The charges are spread all over, since the charges are alike and are trying to get away from one another. The person's hair stands on end as each hair tries to get away from the other hairs. The person is not shocked because they are insulated from the ground--the electricity cannot flow between the ball and the ground. The University of Illinois physics van has this demonstration--kids get to see their teachers with their hair standing up! If you have not seen this demonstration, teachers can contact Dr. Inga Karliner, Physics Department, University of Illinois and we will either come or send you a videotape.

--Dr. Inga Karlinger, High Energy Physics Department, University of Illinois