Using Ohm's law, if a circuit has 12 volts and a resistance of 4 ohms, what is the current?

Ohm's law states V = I × R, where V is voltage, I is current, and R is resistance. To find current, rearrange to I = V ÷ R. Here I = 12 volts ÷ 4 ohms = 3 amps. Ohm's law is the single most important relationship in basic electronics, and you should be able to solve for any of the three variables: V = IR, I = V/R, and R = V/I. A common error is multiplying instead of dividing (12 × 4 = 48). The current in this circuit is 3 amperes.