How do you calculate the B field outside a solenoid from Ampere's law or Biot-Savart law?
I can do it for an infinite solenoid. In that case you just do a loop on the outside and show that since the B field is zero at infinity, it must be zero anywhere outside the infinite solenoid. From that you can calculate the field inside by saying the entire field must come from inside because we found it to be zero outside.
This doesn't work in a finite solenoid. What do I do? Can anybody recommend any references?
