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 :

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

Choose the correct answer: