When the wire is bent in form of a closed circle, the wires will be connected in parallel.
As shown in the figure below.
Also, the resistance will become half because resistance is directly proportional to the length and the length is halved.
Resistance of each part connected in parallel = 5Ω. As shown below.
Resistance of parallel combination
\(\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}\)
⇒ \(\frac{1}{R_{eq}}=\frac{1}{5}+\frac{1}{5}=\frac25\)
⇒ \(\frac{1}{R_{eq}}=\frac{1}{5}=2.5\) Ω
Hence the resistance between ends of the diameter is 2.5Ω.
