The drift velocity of electrons in a conductor is 'v' when a current 'i' flows through it. If the area of the cross-section of the conductor is reduced to half of its initial value, then the drift velocity will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (2) → $v$
Drift velocity is given by:
$v_d = \frac{I}{n e A}$
Where $I$ = current, $n$ = electron density, $e$ = electron charge, $A$ = cross-sectional area.
If the area is reduced to half: $A' = \frac{A}{2}$, keeping current $I$ constant, then the new drift velocity $v'$:
$v' = \frac{I}{n e A'} = \frac{I}{n e (A/2)} = \frac{2I}{n e A} = 2v$
Final Answer: $v' = 2v$