When a current I is set up in a wire of radius r, the drift velocity is `v_(d)`. If the same current is set up through a wire of radius 2r, the drift speed will be
A. `0.25 v_(d)`
B. `0.5 v_(d)`
C. `2 v_(d)`
D. `4 v_(d)`

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1 Answers

Correct Answer - A
`v_(d) prop(1)/(r^(2)) :. V_(d1)r_(1)^(2)=v_(d2)r_(2)^(2)`
`:.v_(d2)=((r_(1))/(r_(2)))^(2) v_(d1)= ((r)/(2r))^(2) vd=0.25 v_(d)`

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