Question

A wire of resistance of 8 ohm is bent to form a circle what is the effective resistance between the ends of the diameter of this circle

Answer 1

the lenght of wire between the two points at the ends of a daimeter will be half of the total circle 
resistance of a wire between the points is 8/2 =4 ohm 
the two section is R we have 1/req =1/4 +1/4 = 2/4 =2 ohm

Answer 2

ans : 2.5 omh is needed