A long solenoid has n turns per unit length and is carrying a certain current i. An electron moves with speed v inside the solenoid in a circle of radius r perpendicular to the solenoid axis. Find an expression for the current i in terms of the given variables. (Use any variable or symbol stated above along with the following as necessary: me for the electron mass, e for the elementary charge, ?0 for the permeability of free space.) i =