A long solenoid (cylinder wrapped with many turns of wire) creates a magnetic field inside of it equal to B=µnI, where µ=4π*10^-7, m/A is the number of turns of wire per unit length, and I is the current in the wire. If the solenoid is very long, then outside (far from the ends) the field is zero.

a. Consider a solenoid with 100 turns of wire per cm (n=100cm^-1). If a current of 2A runs through it, what is the field inside?
b. Let the radius of the solenoid be R1= 2 cm, the radius of a small loop inside it be R2= 1 cm and the radius of a big loop outside it be R3= 5 cm. find the flux through the two loops.
c. Now suppose that the current is decreased at a constant rate from 2A to zero over a time of .2 seconds. What is the EMF induced in (around) each of the two loops (if there were breaks in them)?