Physics Current Electricity Electric Conduction, Ohm's Law, Electric Current, Potential Deffrence Single Correct MCQ
Published on: September 12, 2026

The drift velocity does not depend upon

A
Cross-section of the wire
B
Length of the wire
C
Number of free electrons
D
Magnitude of the current

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Text Solution

Verified by Experts
The correct answer is:
B
Drift velocity (v_d) is defined as the average velocity of charge carriers (like electrons) in a conductor due to an electric field. The equation for drift velocity can be expressed as:
$$ v_d = \frac{I}{nqA} $$
where:
- $I$ is the current
- $n$ is the number density of charge carriers
- $q$ is the charge of the carriers
- $A$ is the cross-sectional area of the conductor

Analysis of Options:
  • Option A: The cross-section of the wire ($A$) does affect drift velocity, as it appears in the denominator of the equation.
  • Option B: The length of the wire does not appear in the formula for drift velocity. Therefore, it does not affect the drift velocity.
  • Option C: The number of free electrons ($n$) directly affects the drift velocity; more electrons would mean a higher drift velocity for a given current.
  • Option D: The magnitude of the current ($I$) is directly proportional to the drift velocity, as seen in the equation.

Therefore, the drift velocity does not depend upon the length of the wire, making Option B the correct answer.

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