Question

AB is a potentiometer wire of length 100 cm and resistance 10 ohms. It is connected in series with a resistance R=40 ohms and a battery of e.m.f. 2 V and negligible internal resistance. If a source of unknown e.m.f. E is balanced by 40 cm length of the potentiometer wire, the value of E is :-

• A. 0.8 V
• B. 1.6 V
• C. 0.08 V
• D. 0.16 V

Answer 1

The correct option is D 0.16 V

$\begin{array}{c}Weknow,\\ E=\frac{e}{\left(R+R_h+r\right)}\frac{R}{L}\times l\\ Now,\\ =\frac{2}{\left(10+40+0\right)}\times \frac{10}{1}\times 0.4\\ =0.16V\end{array}$
Hence, Option $D$ is correct.