Ohm’s Law is a relationship between the voltage, current and resistance of a resistor:
V = I R
where:
V = voltage across the resistor (in volts or V)
I = the current through the resistor (in amps or A)
R = the resistance of the resistor (in ohms or Ω).
The current through the resistor in the diagram at right is 5A. The resistance of the resistor is 3Ω. Substituting these values into Ohm’s Law gives:
V = IR = (5A)(3Ω) = 15V.