question_answer

An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance \[5\Omega .\] The value of R, to give a potential difference of mV across 10 cm of potentiometer wire is- [JEE Main 12-Jan-2019 Morning]

A) \[490\,\Omega \]

B) \[495\,\Omega \]

C) \[395\,\Omega \]

D) \[480\,\Omega \]

Correct Answer: C

Solution :

[c] Let I be the current in the circuit     (i)

According to given condition,

(ii)

Using (i) and (ii), 5+R=400