Question

A potentiometer wire of length 1 m and resistance $10\,\Omega$ is connected in series with a cell

• A. 10000
• B. 19989
• C. 9989
• D. 20000

Answer 1

Answer: (B)

19989

Answer 2

Current in wire = $\frac{10^{-3}}{10} = 10^{-4}$ A
Then, I = $\frac{E}{R + r}$
$i.e.$ $10^{-4} = \frac{2}{ 10 + 1 + R}$
$i.e.$ R = 19989 $\Omega$