Physics · Electric current: drift velocity, mobility and their relation with electric current
Assertion If the length of the conductor is doubled, the drift velocity will bec
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
Step-by-step solution
Drift velocity v_d = I/(nAe). Using Ohm's law, I = V/R, and R = ρL/A, so v_d = V/(n e ρ L). At constant V, v_d ∝ 1/L. Thus doubling L halves v_d. The reason correctly states this inverse proportionality and explains the assertion.
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