Background: When electricity travels through a wire it creates a magnetic field around the wire. Creating the magnetic field requires energy, which is stored in the magnetic field. So, if we have a length L of wire and wrap it in a small loop of say 100 turns, it becomes an air core inductor. However, as a straight wire it's not an inductor. How does looping it make it an inductor? Is the contribution of a small section of looped wire to the magnetic field of the inductor equal to the magnetic field surrounding the same small section of wire when it is straight? Or, does looping make the contribution of each small section greater than it would be if the wire is straight? Another way of phrasing the question is if current I is flowing through the wire of length L is the total energy in the surrounding magnetic field stronger when the wire is looped compared to when it is straight, and if it is, why?