Question

A battery with negligible internal resistance is connected with 10m long wire. A standard cell gets balanced on 600 cm length of this wire. On increasing the length of potentiometer wire by 2m then the null point will be displaced by

• A. 200 cm
• B. 120 cm
• C. 720 cm
• D. 600 cm

Answer 1

Answer: (B)

120 cm

Answer 2

By using $\frac{L_{1}}{L_{2}} = \frac{l_{1}}{l_{2}}$ ⇒ $\frac{10}{12} = \frac{600}{l_{2}}$ ⇒ $l_{2} = 720cm$.

Hence displacement = 720 – 600 = 120 cm