Question

Assertion :In a meter bridge experiment, null point for an unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same point as before by decreasing the value of the standard resistance. Reason: Resistance of metal increases with increase in temperature.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

$X=R\frac{l_1}{l_2}$

As Temperature increases $X$ will increase. To get same null point i.e. same value of $\frac{l_1}{l_2}$, value of standard resistance $R$ should increase.

If the temperature of the metal is raised the atoms vibrate more strongly and the electrons make more violent collisions with them and so the resistance of the metal increase.
Therefore Assertion is false, but Reason statement is true.