Given: A regular hexagon is made of six wires, each of resistance rΩ, and every corner is connected to the centre by a wire of the same resistance. Current enters at one corner and leaves at the opposite corner.
Find: The equivalent resistance between the two opposite corners.
Using symmetry of the network, points placed symmetrically with respect to the line joining the entry and exit corners carry equal currents. Therefore, the current divides equally along identical branches, which allows the network to be reduced by series-parallel combinations.
The solution states that after simplifying the symmetric branches, the equivalent resistance is
Req=54r
Hence, the equivalent resistance between the opposite corners is 54r.
Therefore, the correct option is A.