Question

a wire of resistance 4 ohm is bent to form a circle what is the resistance between two diametrically opposite ends

Answer 1

Given :
Resistance =R=4ohms
Let diameter of circle be AB.
The resistance of upper part will be 2R and lower part of circle will be 2R
The resistance will be in parallel.
R1=R2=2R
1/Rp=1/R1+1/R2
=1/2R+1/2R
=2/2R
1/Rp=1/R 
∴Rp=R ohms 
∴ Resistance between two diametrically opposite ends is R  ohms