question_answer

In the experimental set up of metre bridgre shown in the figure, the null point is obtained at a distance of 40 cm from A. If a \[10\Omega \]resistor is connected in series with \[{{R}_{1}},\] the null point shifts by 10 cm. The resistance that should be connected in parallel with \[({{R}_{1}}+10)\Omega \] such that the null point shifts back to its initial position is- [JEE Main 11-Jan-2019 Evening]

A) \[40\,\Omega \]

B) \[20\,\Omega \]

C) \[60\,\Omega \]

D) \[30\,\Omega \]

Correct Answer: C

Solution :

[c] Case I:              (i)

Case II: or,

or

Case III: Resistance R is connected in parallel with resistance