In a system with several sinusoidal functions, for a definite distinction, in addition to frequency and peak value, the phase angle has to be noted. Two sinusoidal oscillations of the same frequency are deferred with respect to each other, for example:
1. For an ideal coil, inductivity respectively, the electric current of voltage U is shifted back by 90°, only positive reactive power occurs. The phase difference is independent of frequency.
2. For an ideal capacitor the electric current of voltage U is shifted ahead by 90°, only negative reactive power occurs. The phase difference is independent of frequency.
3. For an ohmic resistance, U and I are always in phase. An electric resistor only shows effective power.
4. For a combination of R, L and C the phase shift can have any value between -90° and +90°. The phase difference depends on the frequency and changes notably in proximity to a resonance spot (oscillating circuit).« Back