In some Greek experiments, objects attracted each other after rubbing. Other experiments produced objects that pushed away, or repelled, each other. The evidence showed that electric force made matter either attract or repel other matter.
Electric force is caused by electric charge. Electric charge is a property of the bits of matter within atoms. Electric force can cause matter to attract or repel because there are two kinds of charge – positive and negative charge.
The effects of electric force can be summarized as the law of electric charge: Pieces of matter with the same kind of charge repel each other. Pieces of matter with the same kind of charge attract each other. 2 objects with a positive charge repel each other, as do 2 objects with a negative charge.
Most objects are made of matter with equal amounts of positive and negative charge. Objects with the same # of positive and negative charges are electrically balanced, or neutral. Electric force is observed only when the balance of charge on objects is disturbed.
An electric charge on an object that causes the object to attract or repel other objects is called static electricity. The adjective static describes something that does not move. Charges on an object are called static electricity to contrast then with the moving charges in an electric current.
How can you disturb the balance of charge on objects so they exert electric force? The easiest way is the same way the ancient Greeks did it – by rubbing the 2 objects together. Rubbing neutral objects together allows charged pieces of matter to move from one object to another.
The invisible bits of negatively charged matter that move between objects are called electrons. The words electron, electricity, and electronics all come from the Greek word for amber – elektron. The transfer of electrons explains the electric force that attracts the balloon to the wool. Rubbing the neutral balloon with the wool cloth allows some...
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