1.

A resistance R is to be measured using a meter bridge. Student chooses the standard resistance to be 100 Omega. He finds the null point at I_(1) = 2.9 cm He is told to attempt to improve the accuracy Which of the following is a useful way ?

Answer»

He should measure `I_(1)` more ACCURATELY.
He should change S to 1000 `Omega`and repeat the experiment .
He should change S to `3 Omega` and repeat the experiment .
He should GIVE up HOPE of a more accurate measurement with a meter bridge.

Solution :He should change S to `3 Omega` and repeat the experiment .
To decrease percentage ERROR in resistance R null point of meter bridge should be near the mid point for that value of S should be changed. For balance of bridge,
`(R)/(S) = (l_(1))/(100 - l_(1)) = (2.9)/(100 - 2.9) = (2.9)/(97.1)approx=0.02987`
`therefore S= 100 xx 0.02987= 2.987 Omega`
`thereforeSapprox 3 Omega`
so, option (C ) Is CORRECT .


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