The resistance of the meter bridge AB in given figure is \[4\Omega .\] With a cell of emf \[\varepsilon =0.5V\]and rheostat resistance \[{{R}_{h}}=2\Omega \]the null point is obtained at some point J. When the cell is replaced by another one of emf \[\varepsilon ={{\varepsilon }_{2}}\]the same null point J is found for\[{{R}_{h}}=6\Omega .\] [JEE Main 11-Jan-2019 Morning] |
The emf \[{{\varepsilon }_{2}}\] is |
A) 0.5 V
B) 0.4 V
C) 0.5 V
D) 0.3 V
Correct Answer: D
Solution :
[d] In first case, current flowing through secondary circuit |
Now, once the balance point is achieved, |
.(i) |
Similarly, in the second case, |
.(ii) |
From eqn. (i) |
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