What is the magnetic field inside the solenoid?

Answer: A solenoid is a machine consisting of a long conducting wire packed tightly with numerous wire loops. The conducting wire will produce a magnetic field within and outside the solenoid when an electric current is permitted to run through it. The magnetic field lines inside the solenoid are roughly parallel to one another and uniform, indicating that the magnetic field is also uniform inside the solenoid. We can figure out the equation for the magnetic field within the solenoid by using Ampere’s Law.

The number of turns indicates the solenoid’s total number of loops, N. A stronger magnetic field is created by adding more loops. 

The equation for the magnetic field of the solenoid is   B = m0 I N / L.