Question

What Is Ohm’s Law? Write any two limitations of it.

Answer 1

Hint: Ohm’s Law states the relationship between voltage, current and resistance. All these V, I and R are interrelated to each other either directly or inversely proportional to one another.

Complete step by step solution:
Ohm’s Law states that current is directly proportional to the voltage and inversely proportional to the resistance of the material.
This means when current increases the voltage across it also increases while the resistance of the material decreases. Thus the material allows good flow of current through it.
From the above state we conclude that
$\boxed{I = \frac{V}{R}}$
Where,
 I= Current
V= Voltage
R= Resistance
But there are some exception i.e. Ohm’s Law is not applicable for all the elements. All elements do not follow this V, I and R linear relation.

Limitation of Ohm’s Law:
$\left( 1 \right)$ Ohm’s Law is not applicable for unilateral electrical elements, for example diodes and transistors, as both of them allow the current to flow through in one direction only. While Ohm’s Law is applicable to those elements which allow current in both directions.
$\left( 2 \right)$Ohm’s Law is not applicable to non-linear elements with parameters like capacitance, the voltage and current won’t be constant wrt time.
In this type of element, when we draw voltage versus current graph it is observed that the relation is not linear while according to Ohm’s Law this relation must be linear.


Note:
Before solving any problem related to voltage and current, first keep in mind that all elements that conduct current or voltage across it obey Ohm’s Law. So first check whether the elements follow the Ohm’s Law statement or not, else you will make a mistake.