current squared times resistance
Current = Volts divided by Resistance I = V / R. Resistance = Volts divided by Current R = V / I. According to Wattâs Law : Power = Volts multiplied by Current P = V * I. Power = Current squared times Resistance P = I2 * R. Real world example: Suppose you wanted to figure out how many 500-watt lighting instruments. you could plug into a circuit without blowing a fuse.