Calculating equivalent resistance by Wheatstone bridge concept

Question

I've been learning about the concept of Wheatstone bridge in current electricity chapter. I attempted to solve this problem by that concept:

I don't know if my method is right. I tried to take the resistances inside the dotted lines as one unit( represented by a box) :

Since all the resistances have the same value and by Balanced WB , the 'box' is neglected. However I feel like this is a wrong method. Is it so ? If not please state an alternate formulae ( the question is to calculate equivalent resistance between A and B where all resistance are same

aneet kumar · Answer

The network is symmetric about the line joining points A and B. This implies no current would flow through the resistors which are perpendicular to the line joining A and B.

Bernhard · Answer

You cannot replace the dashed bounding box with one equivalent resistance in your second picture. The box in the first picture has four wires connected to it, while your replacement only has two. Essentially this means that you have assumed the resistances at the top and bottom of your box to be zero. This contradicts with your statement that they are all equal.

Answered by Bernhard on May 5, 2021

relayman357 · Answer

You need to apply the delta-wye transformation back and forth (combining resistors when you can) until you have simplified the circuit to a single resistance between A and B.
The Wheatstone Bridge method is used to determine the value of an unknown resistor. It is not a method for practical use in solving circuits like this.

Calculating equivalent resistance by Wheatstone bridge concept

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