Pascal Vuylsteker
I would like to add unities and understanding of their relations for electrician : V for voltage, VA for VoltAmpere VAR for VoltAmpere Resistif and their relation : V x I => W
Ideally, first letter of a variable would select the appropriate unity according to the following convention
P => Puissance Active (Activ Power) => W
Q => Puissance Réactive (Reactive Power) => VAR
S => Puissance Apparente (Apparent Power) => VA
and as Well ...
F : Farad for Capacity
H : Henry for Inductance
...
Voltage (U) - Volt (V)
Measures the electrical potential difference between two points.
Current (I) - Ampere (A)
Measures the amount of electric charge flowing per second.
Resistance (R) - Ohm (Ohm)
Opposition to the flow of electric current.
Conductance (G) - Siemens (S)
Inverse of resistance: G = 1/R.
Active Power (P) - Watt (W)
Real power consumed by a load: P = U
I
cos(phi).
Apparent Power (S) - Volt-Ampere (VA)
Total power supplied: S = U * I.
Reactive Power (Q) - Volt-Ampere reactive (VAR)
Power related to magnetic and electric fields: Q = U
I
sin(phi).
Capacitance (C) - Farad (F)
Amount of electric charge stored per volt applied: C = Q/U.
Inductance (L) - Henry (H)
Ability of a coil to oppose changes in current: U = L * (di/dt).
Frequency (f) - Hertz (Hz)
Number of cycles per second of a periodic signal.
Energy (E) - Joule (J)
Electrical energy consumed: E = P * t.
Tip: F (Farad) and H (Henry) are complementary in AC circuits: the first acts on the electric field, the second
on the magnetic field.