A capacitor is a device that resists a change in voltage, proportional to current and inversely proportional to capacitance.

dv/dt = i/c

An inductor is a device that resists a change in current, proportional to voltage and inversely proportional to inductance.

di/dt = v/l

In an AC circuit with capacitive loading, the current waveform will lead the voltage waveform; while with inductive loading, the current waveform will lag the voltage waveform.

A plain mag coupler uses magnets to replace the field and armature coils in a brushless dc motor. Then two shafts are coupled together, but to remain coupled they have to be synchronous (rotating at the same speed). If one shaft has a drive motor and the other has the load (fan blades for example) if the load exceeds the maximum torque they slip and are no longer coupled together (the blades will stop turning until the motor stops and restarts).

A mechanical inductive coupling has a squirrel cage similar to an induction motor. This allows the transmission of torque without having to have the same speed.

Also, inductive coupling can refer to transmitting electrical power through coupled inductors or a transformer.

control coupling

content coupling

common coupling

data coupling

external coupling

message coupling

There are many like flexible coupling, jaw coupling, sleeve coupling, tire coupling, pin and bush coupling, rigid coupling, etc