2024 Re-NEET Current ElectricityDrift velocity and current Medium Question 14 of 130 in Current Electricity

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

A $4v$
B $8v$
C $v$
D $2v$

The answer is B.

Solution

$i=nAv_de\propto D^2v_d$. $\dfrac{i_2}{i_1}=\left(\dfrac{D_2}{D_1}\right)^2\dfrac{v_2}{v_1}\Rightarrow\dfrac{200}{100}=\left(\dfrac{1}{2}\right)^2\dfrac{v_2}{v}\Rightarrow v_2=8v$.

Concept Drift velocity and current

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130 questions from this chapter have appeared across 27 exam years.