Find the equivalent resistance between terminals A and B of the resistor network shown (each resistor has value R, in a standard bridge/ladder configuration).

7R/12
7R/5
5R/6
5R/12

Correct answer: 7R/12

Solution

Systematic series-parallel reduction of the network (using symmetry/bridge balance) gives an equivalent resistance of 7R/12 between A and B.

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