Ohm’s Law and High Currents – Rankers Physics
Topic: Current Electricity
Subtopic: Combination of Resistors

Ohm’s Law and High Currents

Assertion (A): Ohm's law holds only for small currents in metallic wire not for high currents.
Reason (R): For metallic wire resistance increases with increase in temperature.
 
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution:

Ohm's law (\(V=IR\)) applies when resistance is constant. For metallic wires, high currents cause significant Joule heating (\(P=I^2R\)), increasing the temperature. This temperature rise increases the wire's resistance, making \(R\) non-constant. Therefore, both assertion and reason are true, and the reason correctly explains why Ohm's law deviations occur at high currents.

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