Question

a wire of resistance. 20ohm is bent in form of a closed cirle what is the effective resistance b/w 2 point at the end of diameter

Answer 1

along the diameter, the circle divides into two equal halves,
therefore resistance of each part is 10 Ω

since both the parts are connected in parallel, the effective resistance=

1/R = 1/A + 1/B
1/R = 1/20 + 1/20
1/R = 1/10
R=10
therefore the effective resistance between the diameter is 10 ohm