Ohm’s law is a Basic Electrical and Electronics Engineering law which relates current, voltage and resistance in a circuit.

Statement: The current in a resistive circuit is directly proportional to the applied voltage and inversely proportional to its resistance.

Mathematical Formula,

I = V/R


  • I = Current in amps
  • V = Voltage in volts
  • R = Resistance in ohms

Consider a resistor R connected to a voltage source V:

If a voltage source V drives an external circuit having resistance R, then, in accordance with Ohm’s law current V/R will flow through it.

Example 1: Let’s assume V = 10 V, and R = 15 ohms, then current I is:

I = V/R = 10 V /15 ohms = 0.66 amps

Provided that there are two known factors, one can compute the third factor by using Ohm’s law equation. 9 different problems in this scenario are illustrated here.

  1. Left column provides method to find current from voltage & resistance
  2. Mid column presents method to calculate resistance provided voltage and current are known
  3. Right column illustrates computation of voltage from resistance and current (amps)