Question

The length of a wire of a potentiometer is 100 cm and the emf of its standard cell is E volt. It is employed to measured emf of a battery whose internal resistance is 0.5 W. If the balance point is obtained at l = 30 cm from the positive end, the emf of the battery is -

• A. 0.2 E
• B. 0.3 E
• C. 0.4 E
• D. 0.5 E

Answer 1

Answer: (B)

0.3 E

Answer 2

e = $\frac{\varepsilon_{0}\mathcal{l}}{L}$ \ e = $\frac{E}{100} \times 30$

\ e = 0.3 E