Four wires each of same length, diameter and material are connected to each other to form a square. If the resistance of each wire is R, then equivalent resistance across the opposite corners is:
Given, resistance of each wire is R.
We have to calculate the resistance from A to B,
Since wire AP and PB are in series, the equivalent resistance across the path APB is R + R = 2R;
also, wire AQ and QB are in series, therefore resistance across path AQB is R + R = 2R
therefore, Reff(APB) = 2R
and Reff(AQB) = 2R
APB is in parallel with AQB, therefore the equivalent resistance across them ⇒1R′ = 12R + 12R
⇒R′=R