Question

Assertion :If the length of the conductor is doubled, the drift velocity will become half of the original value (keeping potential difference unchanged). Reason: At constant potential difference, drift velocity is inversely proportional to the length of the conductor.

• 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. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

The drift velocity is given as,

$u=m\sigma V/\rho efl$, where $m$ is the molecular mass of material,

$\sigma$ is the electric conductivity of the medium at the temperature considered.

$V$ is the potential difference across conductor.

$\rho$ is the the density (mass per unit volume) of the conductor.

$e$ is the elementary charge, in C.

$f$ is the number of free electrons per atom.

$l$ is the length of conductor.

So at constant voltage, the drift velocity is inversely proportional to the length of the conductor.

So If the length of the conductor is doubled, the drift velocity will become half of the original value.

So both the assertion and reason are correct and reason is correct explanation of assertion.