Question

A wire of resistance 5 ohm is bent in the form of a closed circle. What is the effective resistance between the two points at ends of any diameter of the circle?

Answer 1

Resistance of each half circle will be 2.5 ohm

Resistance between two diametrically opposite end, the wire will be in parallel connection.

(1/R) = (1/2.5) +(1/2.5)
         =2/2.5
⇒R = 2.5/2
⇒R= 1.25 ohm 

Answer 2

Answer:

The length of the wire between two points at the ends of a diameter of a circle is

half of the whole wire. The resistance of a conductor is directly proportional to its

length.

Thus, the two resistance 5/2  ohm will be in parallel.

Let R be the effective resistance.

1/R=2/5+2/5

1/R=4/5

R=5/4=1.25 ohm.