A solenoid of 200 loops of wire that cover a length of 0.1 m. The solenoid carries a current of 4.0 A. What is the strength of the magnetic field inside the solenoid?

In this instance do I assume that this time r is 200 x 0.1? Or is it still just 0.1 and I ignore the 200?

4 answers

the magnetic field of a solenoid can be found by placing a square amperian loop around one side of the solenoid. B = N/L*permeability const* current.
N = 200
L = 0.1m

mu = 4*pi*10^-7, n = N/L

B=mu*n*I
A = pi*r^2
//going further
Flux = B*A*cos90 // cos90 = 1
I = 4A
**
cos0 = 1, cos90 = 0
The flux would be dependent on how the magnetic field lined up with the plane