The resistance of the meter bridge 
in given figure is 
. With a cell of emf 
and rheostat resistance 
the null point is obtained at some point J. When the cell is replaced by another one of emf 
the same null point J is found for 
. The emf 
is:
A
B
C
D
Text Solution
Verified by ExpertsThe correct answer is:
B
JEE Main 2019
Given, Emf of cell, 
Rheostat resistance, 
Potential gradient is
Let null point be at 
when cell of emf 
is used.
thus, 
For resistance 
new potential gradient is 
and at null point
Dividing equation 
by 
we get
thus 
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