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A square loop made of wire, each side having resistance 3 ohm, is reshaped into a full circle without changing the total wire length. Find the resistance (in ohm) measured between two points that lie at the ends of a diameter of the circle.

1. 1.5
2. 3
3. 6
4. 12

Correct answer: 3

Solution

The full loop has resistance 12 ohm. A diameter divides it into two semicircular arcs of 6 ohm each, which are in parallel, giving 3 ohm.

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