Question

A Daniel cell is balanced on 125 cm lengths of a potentiometer wire. Now the cell is short circuited by a resistance 2Ω  and the balance is obtained at 100 cm. The internal resistance of the Daniel cell is

• A. 0.5 Ω
• B. 1.5 Ω
• C. 1.25 Ω
• D. 4/5 Ω

Answer 1

Answer: (A)

0.5 Ω

Answer 2

r = $\left( \frac { \ell _ { 1 } } { \ell _ { 2 } } - 1 \right)$R

= $\left( \frac { 125 } { 100 } - 1 \right)$ 2 = 0.25 × 2 = 0.5 Ω