They are a teaching aid for showing students how the various planets revolve and rotate. With an Earth/Moon/Sun system model you can answer all these questions by just turning the handle.. 1  Why we have day and night.  What a year is.
The precursor of any lightning strike is the polarization of positive and negative charges within a storm cloud. The tops of the storm clouds are known to acquire an excess of positive charge and the bottoms of the storm clouds acquire an excess of negative charge.
How to Produce Static Electricity. Static electricity occurs when an electrical charge builds up due to friction between two different objects, usually items that are not good at conducting electricity. You've probably had static electricity in your clothes and hair when they were clingy. The following shows you a few ways to produce static electricity.