Ohm’s Law and Joule’s Law are commonly used in calculations dealing with electronic circuits. These laws are straightforward, but when you’re trying to solve for one variable or another, it is easy to get them confused. The following table presents some common calculations using Ohm’s Law and Joule’s Law. In these calculations,

  • V = voltage (in volts)

  • I = current (in amps)

  • R = resistance (in ohms)

  • P = power (in watts)

    Unknown Value Formula
    Voltage V = IR
    Current I = V/R
    Resistance R = V/I
    Power P = VI or P = V2/R or P = I2R