Problem 4. A. veryr long solenoid of length L and radius R has n turns per unit lengthI carries current I, and is oriented along the z axis. The magnetic eld is: {;L[|H1i, inside I] . 011 f. side (a) [20 points] For a brief period the current varies with time according to I\") : [110.fo where T is a constant. Determine d1e EMF induced by this magnetic eld in the solenoid. (b) [10 points] Determine an expression for the selfinductance L of this solenoid. (c) {10 points] Suppose the current now stops varying with time. Find the energy stored in this solenoid