A Wheatstone bridge is
an electrical circuit used to find the unknown resistance very precisely by
comparing it with a known value of resistances. In this bridge null or balanced
condition is used to find the resistance.
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| WHEATSTONE BRIDGE AT BALANCED CONDITION |
From the figure,
Applying Kirchhoff's loop law in ABD,
I1R1=I2R3 (since
IG=0)
Applying Kirchhoff's loop law in BDC,
I1R2=I2Rx (since IG=0)
\[\therefore \frac{R_{x}}{R_{3}}=\frac{R_{2}}{R_{1}}\]
From the above equation Rx can be computed from the known
value of resistance R3 and the ratio of R2/R1.
Therefore, most of the cases R2 and R1 values are fixed
and the R3 value is variable so that null value is achieved and the
bridge gets balanced.
