A wire of resistance$20 \Omega$ is bent in the form of closed circle. The effective resistance between two points at the ends of any diameter of the circle is _____ $\mathrm{\Omega }$.

Calculate the effective resistance (in ohms) between A and B.

Calculate the effective resistance between A and B. Also find the reading of ammeter and voltmeter.

A piece of wire of resistance $20 \Omega$ is drawn out so that its length is increased to twice its original length. Calculate the resistance (in ohms) of the wire in this new situation.

(Choose among the following: $40 /80 /400$)