NEET Physics Question - Current Electricity - Variation of Resistance with Temperature

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.

(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)

(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(3) (A) is true but (R) is false

(4) Both (A) and (R) are false

Solution:

Concept: Ohm's law states \(V = IR\) with constant \(R\). Resistance of metals depends on temperature.
Formula: \(R_T = R_0(1 + \alpha T)\).
Solution: For high currents, metallic wires heat up significantly, increasing their resistance. This violates the constant resistance assumption of Ohm's law. Therefore, Ohm's law holds for small currents where heating is negligible. A and R are true, and R explains A.

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Solution:

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