Q. 53.6( 11 Votes )

State Ohm's law and mention its limitations.

Answer :

Ohm’s Law

The current flowing through a conductor is directly proportional to the potential difference applied across its ends, provided the temperature and the other conditions remain unchanged.


Potential difference Current


V I


Where,


V= potential difference


I= current


So,



The proportionality constant R is called the resistance of the conductor.


The value of R is independent of V and I but depends upon the conductor


Ohm’s law may also be expressed as




Limitations of Ohm’s law


We may observe two limitations of ohms law in the statement of Ohm’s law itself


(i) Ohms law is only valid for conductors


The conductors that obey Ohm’s law are called ohmic conductors.


Ohm’s law may be obeyed by many substances but it’s not a fundamental law.


Semiconductors and insulators do not obey ohm’s law.


(ii) Its valid only if temperature and other conditions remain unchanged.


If temperature varies then resistance is no longer constant and hence ohms law is invalid.


One more limitation is


(iii) That when the voltage is very high, then a breakdown may occur and ohm’s law fails.


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