B is the magnetic field, in teslas, at any point on the axis of
the solenoid. The direction of the field is parallel to the solenoid axis.
μ_{o} is the permeability constant (1.26x10^{6}
H/m or Tm/A, 1.26x10^{4} Tcm/A or 4.95x10^{5} Tin/A for
coils measured in meters, centimeters and inches, respectively)
i is the current in the wire, in amperes.
n is the number of turns of wire per unit length in the solenoid.
r_{1} is the inside radius of the solenoid.
r_{2} is the outside radius of the solenoid.
x_{1} and x_{2} are the distances, on axis,
from the ends of the solenoid to the magnetic field measurement point.
Note that the units of length may be meters, centimeters or inches (or
furlongs for that matter), as long as the correct value of the permeability
constant is used.
