A : The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased.
R: On increasing temperature, conductivity of metallic wire decreases.

Options

A. Both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. Both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.
C. Assertion is true, but the Reason is false.
D. Both Assertion and Reason are false.

Answer

B

Explanation

(B) b
In `v_(d) = a tau, tau ` is the relaxation time and a is acceleration. As temperature increase `tau` decreases, so `v_(d)` also decreases.
Conductance of metal is `sigma = (l)/(RA)`
As temperature increases R increases and `sigma` decreases . So Reason is also correct but it is not the correct explanation of Assertion.