CUET · PHYSICS · PYQ PAPER 2023

Find the true statement:

A Ohm's law is applicable to diode.
B Resistance of a Incandescent lamp decreases when it is switched on.
C Resistivity of a wire depends on its dimensions
D Resistance of carbon decreases with the increase of temperature.

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Answer & Solution

Correct Answer

(D) Resistance of carbon decreases with the increase of temperature.

Step-by-step Solution

Detailed explanation

Carbon behaves like a semiconductor with a negative temperature coefficient, meaning its resistance drops as heat liberates more charge carriers. Conversely, metals increase in resistance when heated, and resistivity (Option C) is an intrinsic material property that does not…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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