A wire of length 100 cm is connected to a cell of emf 2 V and negligible internal resistance. The resistance of the wire is `3 Omega`. The additional resistance required to produce a potential drop of 1 milli volt per cm is

Options

A. `60 Omega`
B. `47 Omega`
C. `57 Omega`
D. `35 Omega`

Answer

C

Explanation

`l = 2/(3 + R)`
`V/L = 1/100 ((2 xx 3)/(3 + R)) rArr 10^(-3) = 1/100 (6/(3 + R))`
`rArr 3 + R =60 rArr R = 57 Omega`