ExamBro
ExamBro
JEE Mains · Physics · STD 12 - Current electricity
  • JEE Mains 2022
  • Hard
  • MCQ

\(A\). The drift velocity of electrons decreases with the increase in the temperature of conductor. \(B\). The drift velocity is inversely proportional to the area of cross-section of given conductor. \(C\). The drift velocity does not depend on the applied potential difference to the conductor. \(D\). The drift velocity of electron is inversely proportional to the length of the conductor. \(E\). The drift velocity increases with the increase in the temperature of conductor. Choose the correct answer from the options given below:

Pick an option to check your answer.
Verified Solution

Answer & Solution

Correct Answer

(B) \(A\) and \(D\) only

Step-by-step Solution

Detailed explanation

Drift velocity \(=\left(\frac{ e \tau}{ m }\right) E\)

\(v _{ d }=\left(\frac{ e \tau}{ m }\right)\left(\frac{\Delta V }{\ell}\right)\)

\(\Delta V=\) Potential difference applied across the wire

As temperature increases, relaxation time decreases, hence \(V _{ d }\) decreases.

As per formula, \(V _{ d } \propto \frac{1}{\ell}\)

\(v _{ d }=\frac{ I }{\text { neA }}\), as it is not mentioned that current is at steady state neither it is mentioned that \(n\) is constant for given conductor. So it can't be said that \(v _{ d }\) is inversely proportional to \(A\).

\(I=n e A v_{d}=\frac{V}{R}=\frac{V}{\rho \ell} A\)

\(v _{ d }=\frac{ V }{\rho \ell \text { ne }} \quad\left( E =\frac{ V }{\ell}\right)\)

\(v _{ d }=\frac{ eE \tau}{ m }\)

\(\tau\) decrease with temperature increase.

First and fourth statements are correct.

Same subject
Explore more questions on app