The electric resistance of a particular wire of iron is \(R.\) If its length and radius are doubled, then:

Resistances \(n,\) each of \(r~\text{ohm},\)  when connected in parallel give an equivalent resistance of \(R~\text{ohm}.\) If these resistances were connected in series, the combination would have resistance in \(\text{ohms}\) equal to:
1. \(\dfrac{R}{n^2}\)
2. \(\dfrac{R}{n}\)
3. \(nR\)
4. \(n^2R\)

When a wire of uniform cross-section a, length l, and resistance R is bent into a complete circle, the resistance between any two diametrically opposite points will be:

1. R/2

2. R/4

3. R/8

4. 4R