Q.

The figure shows a circuit having eight resistances of 1Ω each, labelled R1 to R8, and two ideal batteries with voltages ε1=12V and ε2=6V.             [2022]

Which of the following statement(s) is(are) correct

1 The magnitude of current flowing through R1 is 7.2 A.  
2 The magnitude of current flowing through R2 is 1.2 A.  
3 The magnitude of current flowing through R3 is 4.8 A.  
4 The magnitude of current flowing through R5 is 2.4 A.  

Ans.

(1, 2, 3, 4)

Here we have folding symmetry, so circuit can be redrawn as

By mesh analysis:

In circuit ACO

0.5i1+0.5(i1-i2)+i1-6=0

0.5i1+0.5i1-0.5i2+i1-6=0

2i1-0.5i2=6

8i1-2i2=24                (i)

In circuit ADO

0.5i2+1×i2-12+0.5(i2-i1)=0

2i2-0.5i1=12               (ii)

From (i) and (ii), we get

7.5i1=36

i1=367.5=4.8 A

So, current through 'R1'=i1=4.8 A

Putting i1=4.8 A in (ii), we get

2i2-2.4=12

2i2=14.4i2=7.2 ACurrent through R1=7.2 A

So, current through R2=|i2-i1|2=|7.2-4.8|2=1.2 A

Current through R5=i12=4.82=2.4 A