calculating the magnetic field in solenoid
Just need a question cleared up.
If I had a coil wrapped around a core, and I was calculating the magnetic field of the solenoid using
B = μnI
where n = N/L, I is current and μ is the permeability of my material
N being the number of turns in the coil, and L being the length of the solenoid if there was an air core. Now if I had a steel core, for example, and the core was a large circular shape such that the coil itself only wrapped around a small amount of the core. Would the length L be the length of the solenoid still? (because its defined as turn density) or would it be the length that the magnetic flux takes through the whole core and therefore be the mean length of the core? (much larger than the length of the solenoid).