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Statement A: Ohm's law is not valid for some conditions of voltage and current. Statement B: There do exist materials and devices used in electric circuits where Ohm's law is not valid.

Statement A: Ohm's law is not valid for some conditions of voltage and current. Statement B: There do exist materials and devices used in electric circuits where Ohm's law is not valid. Correct Answer Both statements are true

CONCEPT:

Ohm's law:

  • A conductor through which a current I is flowing and let V be the potential difference between the ends of the conductor. Then Ohm’s law states that

⇒ V ∝ I

⇒ V = IR

where R is called the resistance of the conductor. Resistance depends on the shape, size, and material of the conductor.

Limitations of Ohm's law:

  • Ohm’s law is valid over a large class of materials.
  • There do exist materials and devices used in electric circuits where the proportionality of V and I does not hold. 

The deviations in occurring are one or more of the following types:

  • V is not to be proportional to I for some range of V or I

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  • The relation between V and I depends on the sign of V. 
    • Reversing the direction of V keeping its magnitude fixed does not produce a current of the same magnitude as I in the opposite direction.

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  • The relation between V and I is not unique
    • There is more than one value of V for the same current I 

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EXPLANATION:

  • There are conditions when Ohm's law is not valid, like high current densities that raise the temperature of the conductor. Therefore statement A is correct.
  • There are materials like diodes that do not always follow Ohm's law. Therefore statement B is also correct.
  • Hence, option 1 is correct.

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