Question 366: Current Electricity

Question

In the experimental set up of metre bridge shown in the figure, the null point is obtained at a distance of 40 cm from A. If a 10 $\Omega $ resistor is connected in series with R
1
, the null point shifts by 10 cm. The resistance that should be connected in parallel with (R
1
+ 10) $\Omega $ such that the null point shifts back to its initial position is :
![](https://imagex.cdn.examgoal.net/NnOtiyEgE4MqNefVl/dAnGiysfTEBcUK3y1Cv0d8wlND1ja/db5k3QAG9q65bzDUCLyail/image.png)

Accepted Answer

${{{R_1}} \over {{R_2}}} = {2 \over 3}\,\,$                                      . . .(i)
${{{R_1} + 10} \over {{R_2}}} = 1 \Rightarrow {R_1} + 10 = {R_2}$     . . .(ii)
${{2{R_2}} \over 3} + 10 = {R_2}$
$10 = {{{R_2}} \over 3} \Rightarrow {R_2} = 30\Omega $
&  ${R_1} = 20\Omega $
${{{{30 	imes R} \over {30 + R}}} \over {30}} = {2 \over 3}$
$R = 60\,\Omega $

Answer

40 $\Omega $

Answer

30 $\Omega $

Answer

20 $\Omega $

Answer

60 $\Omega $

Current Electricity

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