1. The problem statement, all variables and given/known data A long solenoid has 100 turns/cm and carries current i. An electron moves within the solenoid in a circle of radius 2.30 cm perpendicular to the solenoid axis. The speed of the electron is 0.04640c (c= speed of light). Find the current i in the solenoid B = permeability constant * i * 100turns/cm for the solenoid without the electron. I guess I need the speed of the electron somewhere. F = ma qvB = m (v^2)/r So we can get B of the circular loop. What do I do next? I don't suppose we just equate these two B's.