Two resistors 
and 
are connected in the gaps of bridge as shown in figure. The null point is obtained with the contact of jockey at some point on wire 
. When an unknown resistor is connected in parallel with 
resistor, the null point is shifted by 22.5 cm toward 
. The resistance of unknown resistor is 
.
Text Solution
Verified by ExpertsA
In a Wheatstone bridge with 
and 
, the null point is found when 
.
Initial balance: 
gives 
.
For standard wire length 
.
When unknown resistance 
is connected in parallel with 
, equivalent resistance becomes 
.
New null point: 
, which simplifies to 
.
Null point shifts 22.5 cm toward Y: 
.
Substituting: 
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