(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

http://img159.imageshack.us/img159/1867/es100wi8.th.png [Broken]http://g.imageshack.us/thpix.php [Broken]

a) Write an expression for V1 and V2 both in time domain and phasor domain (Solved)

b) Write an expression for the current I both in time domain and phasor domain (Solved)

c) Calculate the Power factor of the supply and specify whether it is lagging or

leading (Solved)

d) Specify the type of the reactance (XC or XL)

e) Determine the value of X and hence the corresponding value of L or C

f) Calculate the supply average, reactive and apparent power

g) Draw the phasor diagram of the circuit

2. Relevant equations

f= 250/3

3. The attempt at a solution

a)

V1 = 10sqrt(2)<48 = 9.46+10.51

V2 = 5/sqrt(2)<0 = 3.54

b)

I = v2/r2 = 0.354<0

c)

PF = 0.669, lagging

d)

X is an inductor

e)

VCh2 + Vxl = Vsource

Vxl = 9.46+10.51j - 5/sqrt(2) = 5.93 +10.51j = 12.1<60.6

Zx = Vxl/Is = 12.1<60.6 / 0.354<0 = 16.77+ 29.73j

This tells me that there's a physical impedance associated with the coil, equal in value to 16.77ohms...Meaning that it's not a pure inductor?

To find L:

29.73 = 2*pi*f*L ... 29.73/ (2*pi*250/3) = L = 0.057H

But these results don't add up to the next few parts:

-Active Power-

P(10ohm)=I^2*R=(0.354)^2*10 = 1.25W

P(16.77ohm)=I^2*R=(0.354)^2*16.77 = 2.10W

Total:3.35W

-Reactive Power-

P(XL)=I^2*R=(0.354)^2*29.73 = 3.72VAR

-Apparent Power-

Active+Reactive*j = 3.35+3.72j

which matches:

S=EI=10sqrt(2)<48 * 0.354<0 = 3.35 + 3.72j

Have I done this question correctly? Is it possible that the inductor has a simple resistance component to it?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: AC circuit, mystery impedance

**Physics Forums | Science Articles, Homework Help, Discussion**