Medium MCQ +4 / -1 PYQ · JEE Mains 2022

(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 :

  1. A (A) and (B) only
  2. B (A) and (D) only Correct answer
  3. C (B) and (E) only
  4. D (B) and (C) only

Solution

<p>We know, Resistivity $\rho=\frac{m}{n e^2 \tau}$ <br/><br/> Where $\tau$ is relaxation time As temperature $\uparrow, \tau \downarrow, \rho \uparrow, \mathrm{R} \uparrow, \mathrm{i} \downarrow, \mathrm{v}_{\mathrm{d}} \downarrow$ as $i=$ ne $\mathrm{A} v_{\mathrm{d}}$ <br/><br/>Statement (A) is correct and hence statement (E) is incorrect. <br/><br/>$$ \mathrm{R}=\rho \frac{l}{A}, I=\frac{V}{R}=\frac{V A}{\rho l}=n e A v_d \rightarrow v_d=\text { constant } $$ <br/><br/>For a given $\mathrm{V}, v_{\mathrm{d}}$ is independent of $\mathrm{A}$. Hence, statement (B) is incorrect <br/><br/>Form above $v_d \propto$ V statement (C) is also incorrect. Since $v_d \propto \frac{1}{\ell}$ as seen from above statement, so statement (D) is correct.</p>

About this question

Subject: Physics · Chapter: Current Electricity · Topic: Ohm's Law and Resistance

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