Lightning Flashes

Thunder and Lightning

Thunder and Lightning
Nature's most spectacular display of static electricity is a flash of lightning. Ancient civilizations once believed that thunder and lightning signified the anger of their gods. During a thunderstorm, raindrops and hailstones hurl up and down inside a thunder cloud producing charges of static electricity. Positive charges move to the top of the cloud, negative charges to the bottom. The Earth is positively
charged, so the negative charges in the clouds are attracted downwards. This is why lightning can occasionally strike the Earth. The hottest part of lightning can reach a temperature six times hotter than the surface of the Sun. You can make sparks like flashes of lightning that are not dangerous at all!

Lightning Flashes

Lightning Flashes

• You will need a large plastic bag, a metal tray, plasticine and a metal fork or skewer. It is best to do the experiment on a floor with a vinyl covering.
• Stand the metal tray, centrally on top of the large plastic sheet. Put a piece of plasticine, large enough to use as a 'handle' in the centre of the tray. Make sure it is firmly fixed to the tray.
• Grip the plasticine with one hand. Press down firmly and rotate the tray, vigorously, on the plastic sheet. Do this for at least a minute. Using the plasticine as a handle, lift the tray off the plastic and keep it suspended in the air.

why it works

Lightning Flashes 02

Although electricity can pass through the metal tray, it cannot pass through the plastic. As the tray is rubbed on the plastic, it becomes negatively charged. When the positively charged metal fork is brought close to the tray, the negative charges are attracted to the positive. They pass from the tray to the fork as a blue spark. This is how lightning works.

• With the other hand, pick up the fork and touch the edge of the tray with it. See the blues sparks fly!

Lightning Flashes 03

Bright Ideas

• Rub other materials together. Which become positively charged and which negatively charged? Do they repel or attract each other? Try rubbing a strip of paper with a woollen cloth. Then hang it over a ruler. The ends of the paper will repel each other because they are similarly charged. Rub a plastic pen with the cloth then hold the pen between the ends of the paper. It will attract the paper, pulling the ends together, because plastic has a strong negative charge. (A moving plastic conveyor belt in a factory can create severe static, and static eliminators have to be used to neutralize the charge.) Unlike charges attract. Try using other materials. Keep a record of your results.
• Make a list of materials and the kind of charge created on them - positive or negative.