A potential difference V is applied to a conductor of length L, diameter D. How are electric field E, the drift velocity `v_(d)` and the resistance R affected when (i) V is doubled (ii)L is doubled (iii) D is doubled ?

Explanation

We have , electric field ` E = (V)/(l)`
Drift speed ` = v_(d) = (eE)/(m) tau = (etau )/(m) (V)/(l)`
and resistance `R = rho (I)/(A) = (rho l)/(pi r^(2)) = ( 4 rho l)/(pi d^(2))`
Hence , (i) When V is doubled , E is doubled, `V_(d)` is doubled and R remain same
(ii) When l is doubled , E is halved `v_(sigma)` is halved and R is doubled .
(iii) When d is doubled , E remains same `V_(d)` remain same and R becomes one - fourth.