Four resistances, each of `10 Omega`, are connected to form a square as shown in (Fig. 3.52), find the equivalent resistance between two points on any one side (AB).
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Explanation

Resistance in the path `ADCB = 10 Omega + 10 Omega + 10 Omega = 30 Omega`
This resistance of `30 Omega` is in parallel with `AB(=10 Omega)`
Equivalent resistance, i.e., `(1)/( R)=(1)/(30)+(1)/(10)=(1 + 3)/(30) = (4)/(30)` or `R = (30)/(4) = 7.5 Omega`.