A closely wound, circular coil with radius `2.40 cm` has 800 turns.
(a) What must the current in the coil be if the magnetic field at the centre of the coil is`0.0580 T`?
(b) At what distance `x` from the centre of the coil, on the axis of the coil, is the magnetic field half its value at the centre?

Answer

A, D

Explanation

a. `B-1=(mu_0Ni)/(2R)`
`b. B_2 =(mu_0NiR^2)/(2(R^2+x^2)^(3/2)) given B_2=B_1/2`