A potentiometer wire has a length of 4 and a resistance of 8 ohm. It is connected in series with a cell of e.m.f. 2 V and internal resistance 2 ohm. The potential drop per unit length of the wire is

Options

A. `0.5 V//m`
B. `0.4 V//m`
C. `0.1 V//m`
D. `0.2 V//m`

Answer

B

Explanation

`I= (E)/(R+ r)=(2)/(8+2)=0.2`
`therefore (V)/(L)=(IR)/(L)=(0.2xx8)/(4) = 0.4 V//m`