Combination of Resistors question from NEET 2009 (AIPMT)

Answer: (d)

1. Length $= 2\pi r = 2\pi \times 0.1 = 0.2\pi$ m, so total $R = 12 \times 0.2\pi = 2.4\pi\ \Omega$.
2. Diametrically opposite points: two halves in parallel, $R_{AB} = \dfrac{R}{4}$.
3. $R_{AB} = \dfrac{2.4\pi}{4} = 0.6\pi\ \Omega$
4. So the answer is (d) $0.6\pi\ \Omega$.