Question

A wire of resistance 12 ohms per meter is bent to form a complete circle of radius 10cm. The resistance between its two diametrically opposite points A and B as shown in the figure is

(1) 3Ω 

(2) 6π Ω 

(3) 6Ω 

(4) 0.6π Ω

Answer 1

Correct option (4)

Explanation:

Answer 2

Length of semi-circle L = πr = π(0.1)

∴ Resistance of each semi-circle R = 12 × 0.1π = 1.2πΩ

Equivalent resistance between point A and B 

R_eq = 1.2π∥1.2π = \(\frac{1.2\pi}{2}\) = 0.6πΩ