201902190815 Electric circuit diagrams (Elementary) Q12

The blogger claims no originality of his problem below.

Find the equivalent resistance between nodes $a$ and $b$ .

Circuit0003

Solution.

We notice that some resistors will be short-circuited, as shown below:

Circuit0003Sol001

Then, the circuit will have equivalent resistance

$R_{\mathrm{eq}}=\bigg( \displaystyle{\frac{1}{R}+\frac{1}{R}}\bigg)^{-1}+\bigg( \displaystyle{\frac{1}{R}+\frac{1}{R}}\bigg)^{-1}=R$ .