Find the current in the 17 Ω resistor in the network shown in the figure. The numbers indicate the resistance of each member in ohms.

Question

Answer 1

In the given circuit diagram 2 ohm and 4ohm resistors at the left hand side may be as a whole treated as 6 ohm resistor. Similarly at the right hand side 4ohm and 11 ohm resistors may be as a whole treated as 15 ohm.  After this the whole circuit shows a symmetry where two ends of each of vertical 6 ohm and vertical 15ohm resistors should have same potentials. Hence for calculation of equivalent resistance across A and B the presence of these two vertical resistors becomes irrelevant. So the whole circuit becomes a combination of two parallel resistors one is (6+41+15)=62ohm and another is (6+17+15)=38ohm. Hence the equivalent resistance across AB becomes =R=(62×38/100)ohm

So the main Current

I= 115/R =115×100/(62×38)A

Hence the current through 17 ohm resistor will be

i= I×62/100=115/38 A