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NEET 2024
Exam
NEET
Year
2024
Subject
Physics
Chapter
Current Electricity

NEET 2024 · Physics · Current Electricity

A uniform wire of diameter d carries a current of 100 mA when the...

A uniform wire of diameter dd carries a current of 100 mA when the mean drift velocity of electrons in the wire is vv. For a wire of diameter d2\frac{d}{2} of the same material to carry a current of 200 mA , the mean drift velocity of electrons in the wire is

Options

  1. A4v4 v
  2. B8v8 v
  3. Cvv
  4. D2v2 v

Correct answer

B. 8v8 v

Step-by-step solution

current i=nAvdei=n A v_d \mathrm{e} ( vd=v_d= mean drift velocity )) =n(πD24)vde=n\left(\frac{\pi D^2}{4}\right) v_d e ∴i∝D2vd\therefore i \propto D^2 v_d 100200=(d)2(d2)2×vv′\frac{100}{200}=\frac{(d)^2}{\left(\frac{d}{2}\right)^2} \times \frac{v}{v^{\prime}} ⇒v′=2×22v=8v\Rightarrow v^{\prime}=2 \times 2^2 v=8 v
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