3.9 Determine the current in each branch of the network shown in Fig. 3.30:

Figure 3.30

Current flowing through various branches of the circuit is represented in the given figure.

I1 = Current flowing through the outer circuit

I2 = Current flowing through branch AB

I3 = Current flowing through branch AD

I2 - I4 = Current flowing through branch BC

I3 + I4 = Current flowing through branch CD

I4 = Current flowing through branch BD

For the closed circuit ABDA, potential is zero i.e.,

10I2+5I4-5I3=0
2I2+I4-I3=0
I3=2I2+I4 ...(1)

For the closed circuit BCDB, potential is zero i.e.,

5(I2-I4)-10(I3+I4)-5I4=0
5I2+5I4-10I3-10I4-5I4=0
5I2-10I3-20I4=0
I2=2I3+4I4 ...(2)

For the closed circuit ABCFEA, potential is zero i.e.,

-10+10(I1)+10(I2)+5(I2-I4)=0
10=15I2+10I1-5I4
3I2+2I1-I4=2 ...(3)

From equations (1) and (2), we obtain

I3=2(2I3+4I4)+I4
I3=4I3+8I4+I4
-3I3=9I4
-3I4=+I3 ...(4)

Putting equation (4) in equation (1), we obtain

I3=2I2+I4
-4I4=2I2
I2=-2I4 ...(5)

It is evident from the figure that,

I1=I3+I2 ...(6)

Putting equation (6) in equation (1), we obtain

3I2+2(I3+I2)-I4=2
5I2+2I3-I4=2 ...(7)

Putting equations (4) and (5) in equation (7), we obtain

5(-2 I4)+2(-3 I4)-I4=2
-10I4-6I4-I4=2
17I4=-2
I4=-217A

Equation (4) reduces to

I3=-3I4=-3(-217)=617A
I2=-2I4=-2(-217)=417A
I2-I4=417-(-217)=617A
I3+I4=617+(-217)=417A
I1=I3+I2=617+417=1017A

Therefore, the current in branch in AB=I2=417A

The current in branch in BC=I2-I4=617A

In branch CD=I3+I4=417A

In branch AD=I3=617A

In branch BD=I4=-217A

Total current=I1=1017A