The magnetic field due to a square loop of side a carrying a current I at its centre is
A symmetric star shaped conducting wire loop is carrying a steady state current I as shown the figure. The distance between the diametrically opposite vertices of the star is 4a. The magnitude of the magnetic field at the center of the loop is
A current of I ampere flows along an infinitely long straight thin walled hollow metallic cylinder of radius r. The magnetic field at any point outside the cylinder at a distance x form the axis is