A cube is formed with ten identical resistances $R$ (thick lines) and two shorting wires (dotted lines) along the arms $A C$ and $B D$ as shown in the figure below. Resistance between point $A$ and $B$ is ...........$\Omega$
KVPY 2012, Diffcult
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(a)

First we connect points of equal potentials and redraw equivalent circuit.

Above equivalent circuit is a combination of two balanced Wheat stones bridge.

Hence, simplified circuit is

In above circuit, resistance combination gives,

So, equivalent resistance between $A$ and $B$ is $R_{A B}=\frac{R}{2} \,\Omega .$

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