IIT JEE Advanced 2012 Paper 1

From Wheatstone bridge, since the nodes P and Q are equipotential, then nodes S and T are also equipotential; therefore, no current passes through PQ and ST. Therefore, further simplified network is as shown in the following figure:

I1 =

12

4

= 3 A
I2 = I1(

12

6+12

) = 2 A