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Nishtha Pathak from Narayana Vidyalayam, asked a question
Subject: Physics , asked on 20/5/11

What are the limitations of Ohms Law?

EXPERT ANSWER

Bapan Pathak , Meritnation Expert added an answer, on 13/6/11
585 helpful votes in Physics

Hi Nishtha,
 
Ohm’s Law: The current flowing through a conductor is directly proportional to the voltage applied to across the ends of the conductor.So, the V-I graph for a conductor following the Ohm’s law is a straight line with a positive slope.
 
Limitations of this law:
1.  Now, this law is valid for conductors only and that too at a constant temperature. The resistance of a conductor increases with temperature. Hence, for changing temperature the V-I graph for a conductor will be non-linear (not a straight line).
 
2.  In case of insulators ohm’s law is not followed at all, insulators do not conduct at all. But, when a very high voltage is applied across an insulator dielectric break down occurs and all of a sudden current begins to flow.
 
3.  Ohm’s law is not followed by semiconductors. The V-I graph has a steep rising at a particular voltage, which indicates that the material begins to conduct properly only after a certain voltage.
 
Hope this explanation helps you understand the limitations of the Ohm’s Law.

Do write back if you have any doubt or confusion.
Keep posting & have a nice day!

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