The coupling comprises of two concentric parts, the body or input part containing the field coil within it,separated by small annular gap, an inner rotor, or output part. The annular gap contains a ferromagnetic powder,which is activated when the coil is energized. The resultant flux which is generated, passes through the powder,causing it to align with the flux path, and thereby creates a driving bond between input and output part, thestrength of which is solely determined by value of D.C. current applied to the field coil.
