Ohm’s Law and the Electric Power

Ohm’s Law relates in one equation the voltage, the current and resistance. Resistance = Resistor’s value.

A more complete expression of Ohm’s Law is achieved using the electric power formula. Using the known formula of power: P = VxI, (Power = voltage x current), and its variants: V = P/I and I = P/V, additional equations are obtained.

These new equations allow us to obtain the values of power, voltage, current and resistance, with only two of the four variables.

• Solving for P, we get: P = V²/R, P = I² x R, P = V x I. (watts)
• Solving for I, we get: I = V/R, I = P/V, I = (P/R)^1/2. (amps)
• Solving for R, we get: R = V/I, R = V²/P, R = P/I². (ohms)
• Solving for V, we get: V = (PxR)^1/2, V = P/I, V = IxR. (Volts)

The diagram shows a complete summary of the formulas, arranged so that it is easier to memorize.

Note: The square root = ( )^1/2.