A solenoid is made from a long wire of radius R = 1.00mm. It is wrap on a cylinder of radius 4.00cm and length l = 50cm.
a) how many turns are in a single tightly wound layer?
b) if the solenoid is made of four tightly wound layers, how long is the wire needed for the solenoid?
c) what is the magnetic field within the solenoid if a current I = 4 amps is run through it?