Question

what is the physical meaning of tg(theta) and what is the difference between tg(theta),cos(theta) and power factor in RLC circuit?Provide a graphical explanation for above.

Answer 1

In a RLC circuit with AC currents the voltage and the current are not in phase, there is a phase difference.

Tan() = (X_c - X_L)/R , ratio of reactive load to resistive load.

is the angle by which current leads the voltage.

Cos() = R/ sqrt( R² + (X_c -X_L) ) , is the ratio of resistive load to the total impedence.

In an AC circuit, current and voltage vary with time and also they differ in time, there is a phase difference as seen above depending on the type of load.

The power cannot be computed straight by IV as in the case of DC circuits .

Averaging the instantaneous power over one complete cycle

P = V_rmsI_rms Cos() ,

Cos() is called the power factor.