- #1
Joe85
- 29
- 3
Homework Statement
For the circuit given in the power factor is 0.72 lagging and the power dissipated is 375 W.
Determine the:
(1) apparent power
(2) reactive power
(3) the magnitude of the current flowing in the circuit
(4) the value of the impedance Z and state whether circuit is inductive or
capacitive.
(1) Apparent power = True power / Power Factor (S=P/pf)
= 375 / 0.72
= 520.8333 VA
(2) Reactive Power = SQRT (apparent power^2) - (True Power^2)
= SQRT (520.8333^2)-(375^2)
= SQRT (130642.3264)
= 361.4448 VAR
(3) Magnitude of Current
Power= Voltage*Current *Power factor (P=V*I*pf)
375 = 120*I*0.72
I = P/(V*pf)
I = 375/(120*0.72)
I = 4.34 A
(4) Total ohms = Voltage/Current
= 120/4.34
= 27.6498 ohms
Phi= arccos(0.72) = 43.95
RT = 10 ohms
ZTotal= 27.6498∠43.95
Z = ZTotal - 10 | Cannot subtract complex numbers in polar form.
27.6498(Cos43.95+JSin43.95) = 19.9064 + J19.1898
(19.9064 + J19.1898) - 10 = 9.0964 + J19.1898
Z = SQRT (9.0964^2)+(19.1898^2) = 21.24
Phi = Arctan (19.1898/9.0964) = 64.64
Z = 21.24∠64.64 Lagging
Phase Angle Lagging - Circuit Inductive.
Homework Equations
The Attempt at a Solution
So i borrowed heavily from an older thread as my answers for 1 - 3 are identical. It's part 4 where I'm sturggling a bit. I followed the original thread, went away, refreshed my complex numbers knowledge and have come back with the above.
Would be greatful if someone could validate my answer or tell me if i have completely borked it up and offer some guidence.
Attachments
Last edited: