Ohm’s law states that it takes 1 volt to push 1 ampere through 1 ohm. Ohm realized that all electric quantities will be proportional to each other and can as a result be expressed as mathematical formulas. He discovered that if the resistance of a circuit remained constant and the voltage increased, there was a corresponding proportional increase of current. Similarly, if the resistance remained constant and the voltage decreased, there’d be a proportional decrease of current. He also found that if the voltage remained consistent and the resistance increased, there would be a decrease of current; and any time the voltage remained constant and the resistance decreased, there would be an increase of current. This unique finding led Ohm to the conclusion that in a DC circuit, the current is directly proportional to the voltage and inversely proportional to the resistance.

The three basic ohms law formulas are:

The first formula can be used to find volts, when the current and resistance are known. The second formula can be used to find current, when the volts and resistance are known. The third formula can be used to find resistance, when the volts and current are known.

Another chart can also be used when the power (watts) must be determined.