JEE Main 12 Jan 2019 Morning Question 11
Question: 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 Online Paper Held On 12-Jan-2019 Morning]
Options:
A) $ 490,\Omega $
B) $ 495,\Omega $
C) $ 395,\Omega $
D) $ 480,\Omega $
Show Answer
Answer:
Correct Answer: C
Solution:
-
Let I be the current in the circuit $ 4=(5+R)I $ -(i)
According to given condition, $ 5\times {10^{-3}}=( \frac{10}{100} )(5)(I) $
$ \Rightarrow $ $ I={10^{-2}}A $ -(ii) Using (i) and (ii), 5+R=400
$ \Rightarrow R=395\Omega $
