Watch this Video of magnetic levitation: https://youtu.be/OI_HFnNTfyU; pay attention to the part starting 6230 6. In Question 5(c) above, the magnetic force changes direction periodically just like the changing magnetic eld. But in the videos about magnetic levitation, apparently an alternating magnetic eld always repels conductors in the eld. Why is that? One explanation is the self-inductance. The ring in Question 5 has negligible inductance, thus the induced current is in-phase with the induced emf: I = 97% (R is the resistance of the ring). But for a large piece of metal plate or a large solenoid Whose inductance cannot be ignored, the induced current is delayed relative to the induced emf: emf = L g (L is the self-inductance of the plate or solenoid, the negative sign is missing because the emf here is producing the current). Magneticfield Coilcarrving 4, electric current Now let us replace the ring in Question 5 With a solenoid. Suppose that the alternating magnetic eld can be described as B = 30 cos wt. Deduce an expression for the induced magnetic eld of the solenoid. With your expression, try to explain why the fokce between the alternating magnetic eld and a solenoid is always repulsive. (Math tips: dxx) = sin 2:; (13;?) = cos x)