Question

Find the equivalent resistance between $A$ and $B$.

• A. $2R$
• B. $3R$
• C. $R$
• D. $\frac{R}{2}$

Answer 1

The correct option is C $R$

We can observe a parallel line of symmetry about $AB$ for the given circuit.


Thus points ${}^{\prime }{C}^{\prime }$ and ${}^{\prime }{D}^{\prime }$ will be at same potential, hence resistance connected across them can be neglected.
On redrawing circuit:


All three ${}^{\prime }3R^{\prime }$ resistance are in parallel.

$\Rightarrow R_{eq}=\frac{3R}{3}$

$\therefore R_{eq}=R$