Phasors Passive RL Circuit Response

          In this lab, the steady-state response of an electrical circuits is determined with a 

sinusoidal inputs.The input and output signals both have the same frequency, but the two

 signals can have different amplitudes and phase angles. The analysis of the circuit can be simplified 

by representing the sinusoidal signals as phasors. 

     Elements of series RL circuit are : L = 1mH and R = 47W.Input voltage frequencies:·        w = w_c /10 (low frequency input)
·        w = 10*w_c  (high frequency input)
·        w = w_c  (corner frequency input)

Figure 1: A Series RL Circuit

When frequency increasing the inductor voltage increasing and also phase difference between VL 

and VR, or between VL and I increase because VR is constant under frequency changes. Voltage 

across resistor in in phase with current circuit.

Figure 2: RL series at 1 KHz 

The phase difference is so small in above figure at 1 KHz.

Figure 3: RL Series at 7.1 KHz

The phase difference is so small in above figure at 1 KHz. According to the above grapg, frequency 

is equal with 7.1 KHz.  f = 1 / (140 μs) = 7143 Hz

Also ∆t = (2.5)*(5 μs) = 7.5 μs so ∆φ = (∆t / T) *(360°) , ∆φ = (7.5 / 140)*(360°) = 19.29°

 

Figure 4: A Schematic of  a Series RL Circuit