Using meter bridge, it is advised to obtain the null point in the midd

1.	Using meter bridge, it is advised to obtain the null point in the middle of bridge wire. Why?
Answer» The error in the measured value of unknown resistance S using meterbridge wil be minimum, when the null point is obtained at the middle of meterbridge wire. In this situation, the end error of the bridge will become ineffective. To understand it, let `alpha` be the end resistance of left and right copper strips in meterbridge. Let unknown resistance R be in the left gap of meter bridge. If null point is obtained at the middle of bridge wire (i.e., `l = 50cm`) then `(S + alpha)/(R + alpha) = (100 -50)/50 = 1 or S = R` It means the effect of `alpha` gets cancelled. In this situation the bridge is most accurate ans sensitive. If the null point is not at the centre, there will be some error becasue S will then not be equal to R.

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Using meter bridge, it is advised to obtain the null point in the middle of bridge wire. Why?

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