InterviewSolution
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InterviewSolution
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The Fig. shows experimental set up of a metre bridge. Whenthe two unknown resistances X and Yare inserted, the null point Dis obtained 40 cm from the end A. When a resistance of 10Omegais connected in series with X, the null point shifts by 10 cm. Find the position of the null point when the 10Omegaresistance is instead | А connected in series with resistance ‘Y. Determine the values of the resistances X and Y. |
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Answer» Solution :When two unknown resistances X and Y are inserted as shown in the figure, then null POINT D is obtained at 40 CM from end A i.e., l = 40 cm. ` therefore X/Y = (40)/((100 - 40)) = 40/60` ` rArr Y = 3/2 X`....(i) When a resistance of 10`OMEGA`is connected in series with X, the null point should shift away from point A. As null point SHIFTS by 10 cm, hence `l_1`= 40 + 10 = 50 cm. ` therefore (X+10)/(Y) = (50)/(100 - 50) = 50/50` `rArr X+ 10 = Y`..(II) Solving (i) and (ii), we get X = 20 `Omega`and Y = 30 `Omega`. If a resistance of 10`Omega`is connected in series with resistance Y then the null point will be obtained at a distance `l_2`from point A, such that `(X)/(Y+ 10) = (l_2)/(100 - l_2) " or" (20)/(30 + 10) = 20/40 = (l_2)/(100 - l_2)` ` rArr l_2 = 100/3 cm= 33.3 cm ` |
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