Moving Charges And Magnetism

A straight wire of diameter \(0.4 \mathrm{~mm}\) carrying a current of \(2 \mathrm{~A}\) is replaced by another wire of 0.8 \(\mathrm{mm}\) diameter carrying the same current. The magnetic field at distance \((\mathrm{R})\) from both the wires is 'B\(_1\)' and 'B\(_2\)' respectively. The relation between B\(_1\) and B\(_2\) is