In a wire of cross-section radius `r`, free electrons travel with drift velocity `v` when a current `I` flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is `2v`?

Options

A. 2I
B. I
C. `I//2`
D. `I//4`

Answer

C

Explanation

`I = "ne"Av_(d)`
`I_(1)/I_(2) = ((r_(1))^(2)v_(d_(1)))/((r_(2))^(2)v_(d_(2))) = (r^(2)v)/(r^(2)/4 2v) = 2, I_(2) = I_(1)/2 (I = I_(1))`