A circular coil having 18 tums of wire and immersed in a medium of relative permeability of 135. If the coil has a radius of 33 cm and is in the plane of the paper. What current in unit of Xampere (A) must exist in the coil to produce a flux density of so mt at its center?
Correct Answer 10.81 please explain how

Suppose a diode consists of a cylindrical cathode with a radius of 6.200×10^−2 cm , mounted coaxially within a cylindrical anode with a radius of 0.5580 cm . the potential difference between the anode and cathode is 260 v . an electron leaves the surface of the cathode with zero initial speed (v initial=0). find its speed vfinal when it strikes the anode.