Ohm’s Law is considered very important while studying function of electrical and electronic devices. Ohm’s law simply provides you a relation between voltage, current and resistance of the circuit

All these three factors, voltage, current and resistance are dependent on each other. There is a relation between these factors and that relation is explained by the Ohm’s Law.

Ohm’s Law



What does Ohm’s Law actually states???

The Ohm’s Law states that ‘the current flowing through a circuit is directly proportional to the voltage of the circuit and inversely proportional to the resistance of the circuit.’



We can simply put this relation in a mathematical form shown as below,



I = Current

V= Voltage

R= Resistance

We can express the above mathematical form in a very easy manner as,current is directly dependent on voltage, and inversely dependent to the resistance.

Ohm’s Law



Ø  Current relation with Voltage

When the voltage in the circuit is increased the current in the circuit is also increased vice versa when the voltage in the circuit drops, the current in the circuit also reduces as they are directly proportional as stated above.


Ø  Current relation with Resistance

But when the resistance of the circuit is increased then the current is reduced and if the resistance of the circuit is reduced then the current in the circuit gets increased as they are inversely proportional to each other.



We can find unknown voltage, current or resistance of the circuit, if at least two quantities are known to us. Ohm’s law is essential part of any electrical study. We can manipulate the formula in various manners as given below.


V = I x R 


R = V / I

Ohm’s Law


By using all three parameters of Ohm’s law we can also find the Power consumed in the circuit as Power used in the circuit is the product of current and voltage.



  • We should also keep in mind that Ohm’s law is not applicable in the following conditions,

·         If the resistance of the circuit is varying and not constant then Ohm’s law is not applicable in this condition.


  • ·         If the temperature is not constant then also we cannot apply Ohm’s law to the circuit.


  • ·         Ohm’s law is also not applicable to semiconductors, insulators, vacuum tubes, thermistors, filament bulb, crystal rectifiers etc.

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