From the above equation we can generate an expression for the field of a solenoid infinite in length. In an infinite solenoid there is a uniform magnetic field in the direction of the axis, given by:

B = (cos 0 - cosΠ) =    

This is the magnitude of the uniform field inside the solenoid. The field outside an infinite solenoid is always zero.

The study of these complex wire shapes concludes our study of the sources of magnetic fields. In the next SparkNote in the series on magnetic forces and fields we will take a more theoretical approach to magnetism, describing some of the properties of all magnetic fields.