Drift velocity of electrons in a conductor bearing potential difference V across its terminals is v. If the length of wire is stretched to three times and same potential differece V is applied, then the drift velocity will become

Options

A. `v/3`
B. `v/2`
C. `v/6`
D. v

Answer

A

Explanation

When the wire is stretched to three times, resistance becomes 9 times and area becomes one third.
`:. I=(V)/(R)= n e A v_(d)`
`:.v_(d)=(V)/(R n e A) :.v_(d) prop (1)/(AR)`
`:.(v_(d1))/(v_(d2))=(A_(1)R_(1))/(A_(2)R_(2))=(AR)/((A//3)(9R))=(1)/(3)`
`:.v_(d2)=(v_(d1))/(3)=(v)/(3)`