The ampere-turn (symbol A⋅t) is the MKS (metre–kilogram–second) unit of magnetomotive force (MMF), represented by a direct current of one ampere flowing in a single-turn loop.
[1] Turns refers to the winding number of an electrical conductor composing an electromagnetic coil.
[citation needed] By maintaining the same current and increasing the number of loops or turns of the coil, the strength of the magnetic field increases because each loop or turn of the coil sets up its own magnetic field.
In Thomas Edison's laboratory Francis Upton was the lead mathematician.
Trained with Helmholtz in Germany, he used weber as the name of the unit of current, modified to ampere later: