Electric Measurement

Electric measurement. Electricity itself cannot be observed. But one form of electricity called electric current produces several observable effects, including heat, force, and magnetism. We can use these effects to measure electricity.

Electric current is measured in amperes. An instrument called an ammeter is used to measure electric current. The quantity of electricity carried by an electric current, also known as electric charge, is measured in coulombs. A coulomb is the quantity of electricity transmitted by a current of 1 ampere in 1 second.

Electric current results from a difference in electric potential (potential energy). This difference causes an electric charge to move from one point to another. Electric potential is measured in volts. A volt is defined as the difference in electric potential between two points on a wire that is carrying 1 ampere of current and producing 1 watt of power. A watt is a unit of electric power, and it is measured by a wattmeter. When electric power is delivered to a home or business, it is measured in units called kilowatt-hours. A kilowatt-hour equals the amount of power produced by 1,000 watts in one hour.

The opposition of a material to electric current is called resistance. Electric resistance is equal to the difference in electric potential divided by the electric current. It is measured in ohms. An ohm is the resistance of a conductor carrying 1 ampere of current when the potential difference across the conductor is 1 volt. An instrument called an ohmmeter is used to measure resistance.

Contributor: Raymond D. Findlay, Ph.D., Director, Engineering and Management, McMaster Univ.

Electric Measurement

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