Which of the following graphs represents the variation of magnetic field $B$ with perpendicular distance ' $r$ ' from an infinitely long, straight conductor carrying current?

A square loop of side 2 m lies in the Y-Z plane in a region having a magnetic field $\overrightarrow{\mathrm{B}}=(5 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}-4 \hat{\mathrm{k}}) \mathrm{T}$. The magnitude of magnetic flux through the square loop is

A moving electron produces

A coil having 9 turns carrying a current produces magnetic field $B_1$ at the centre. Now the coil is rewounded into 3 turns carrying same current. Then, the magnetic field at the centre $B_2=$