A second charge will feel a force when placed in an electric field, just like a mass feels a force when placed in a gravitational field. Current is measured with ammeters. Read the text to learn more about potential difference or voltage. For example, a bulb has a given resistance, say 40 W . However, many circuit elements do not obey this law.
Electric power is the product of VI, and is the rate of doing work.
Compasses have N and S written on them. If they represent poles, then our geographic north pole is actually a magnetic south pole in order for the N on the compass to be attracted towards it. Like poles repel. Unlike poles attract. Only dipoles seem to exist in nature.