Problem 1-7: Circuit Reduction - Current Divider


Find  I_9 (Hint: use circuit reduction).
All resistors are  10\Omega and  Is_1=10A
Problem 1-7 - Circuit Reduction


Solution
Let's redraw the circuit:


Circuit Reduction - Redrawing the circuit
The equivalent resistances are:  R_a= R_{10}+R_6+R_{11}+R_8+R_7=50 \Omega

 R_b= R_a ||(R4+R_5)=50 || 20 =  \frac{100}{7} \Omega

 R_c= R_b+R_2+R_3=\frac{240}{7} \Omega

Now, the circuit is reduced to:
Circuit Reduction - Reduced circuit
Using current divider:

 I_9=\frac{R_c}{R_9+R_c} \times Is_1= 7.742 A


3 thoughts on “Problem 1-7: Circuit Reduction - Current Divider

  1. kane

    In this case (r2+r3)//(r4+r5).. so why cant we apllly the current divider rule to this.???
    please explain...

    Reply
    1. Dr. Yaz Z. Li

      Those two branches are not in parallel. They would be parallel if R9 was a short circuit. So, if you replace R9 with a short circuit, Rnew=(R2+R3)||(R4+R5) with one node connected to the left node of R10 and the another one connected to the left of R7.

      Reply

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