In Electrical engineering we have Cosine ø = a Power factor in an electrical circuit. What kind of a circuit is this? Explain this in Brief?

In any circuit that has a coil or capacitor there must be a power factor CoSine Φ. because Φ is the phase shift between voltage and current in a vector analysis and each of a coil or capacitor makes a difference between V & I. so any circuit must have a power factor that is less then1.

the only circuit that has no power factor (has a power factor that equals1) is:

1- circuit with only resistances. (no coil, no capacitor).

2- Resonance circuit (a circuit with inductance exactly equals capacitance as each eliminate the other).