A wire carrying current $I$ is bent into a semicircle of radius $R$ with straight leads extending to infinity. The magnetic field at the center of the semicircle is:

A current loop has magnetic moment $\vec{m}$. Far from the loop on its axis ($x \gg R$), the magnetic field varies as:

Two concentric coplanar circular loops of radii $R$ and $2R$ carry currents $I$ and $I$ respectively in opposite directions. The magnetic field at the center is:

A wire is bent into a shape consisting of a quarter circle (radius $R$) and two straight segments passing through the center. The field at the center due to the entire wire is:

A circular coil of 10 turns and radius 0.1 m carries a current of 2 A. The magnetic field at the center is: