while using meter bridge,it is advised to obtain null point in the middle of wire,why
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At the middle point generally the meter bridge will be more sensitive compared to any other position . So, if you will obtain a balance point in the middle then there will be more accuracy and minimum occurance of error
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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. To understand it, let α 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+α/R+α=100−50/50=1orS=R
It means the effect of α 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.
Explanation:
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