Question

A potentiometer wire of length 10 m and resistance 20 Ω is connected in series with a 25 V battery and an external resistance 30 Ω. A cell of emf E in secondary circuit is balanced by 250 cm long potentiometer wire. The value of E (in volt) is $\frac {x}{10}$. The value of $x$ is ______.

Answer 1

$E = I \times (\frac {20}{4})$

$E= \frac {25}{(30+20)} \times (\frac {20}{4})$

$E= \frac 12 \times 5$

$E= 2.5$ volts

$E= \frac {25}{10}$ volts
Given that, The value of E (in volt) is $\frac {x}{10}$.
On comparing,
$x = 25$
So, the answer is $25$.