Attraction and repulsion
Opposite (unlike) charges Objects that tend to move together because of a force between them attract each other. one another. Like charges Objects that tend to push apart because of a force between them repel each other. one another.
This is often demonstrated using plastic rods charged with a duster.
Image caption, Two identical plastic rods have like charges. The hanging rod turns away from the other rod.
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Demonstrating charge
The only way to tell if an object is charged is to see if it repels another charged object. This is because a charged object can attract an uncharged insulator.
For example, a negatively charged plastic object such as a comb or ruler repels electrons in a piece of paper. The near side of the paper to the plastic object becomes positively charged, so it is attracted to the plastic object. This is why party balloons attract hair after they have been rubbed on a shirt or jumper.
