What is Ohm’s Law?

Ohm’s Law is a formula used to calculate the relationship between voltage, current, and resistance in an electrical circuit. This law states the relationship between electric current and potential difference. The current that flows through most conductors is directly proportional to the voltage applied to it. Georg Simon Ohm is a German physicist who was the first to verify Ohm’s law experimentally.

Ohm's Law

where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, It is an empirical relation that accurately describes the conductivity of the vast majority of electrically conductive materials over many orders of magnitude of the current. However some materials do not obey Ohm’s law, these are called non-ohmic.

Mathematically, this current-voltage relationship can be written as,


In certain components, increasing the current raises the temperature. An example of this is the filament of a light bulb, in which the temperature rises as the current is increased. In this case, it cannot be applied. The lightbulb filament violates Ohm’s Law.

Ohm’s Law Solved Problem: 1

If the resistance of an electric iron is 50 Ω and a current of 3.2 A flows through the resistance. Find the voltage between two points.


If we are asked to calculate the value of voltage with the value of current and resistance given to us, then cover V in the triangle. Now, we are left with I and R or more precisely I × R.

Therefore, we use the following formula to calculate the value of V:

V = I × R

Substituting the values in the equation, we get

V = 3.2 A × 50 ÷ = 160 V

V = 160V

Applications of Ohm’s Law

  • To determine the voltage, resistance, or current of an electric circuit.
  • Used to maintain the desired voltage drop across the electronic components.
  • It is also used in DC ammeter and other DC shunts to divert the current.

Limitations of Ohm’s Law

  • It is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
  • For non-linear electrical elements with parameters like capacitance, resistance, etc the voltage and current won’t be constant concerning time making it difficult to use Ohm’s law.

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