• Support PF! Buy your school textbooks, materials and every day products Here!

I need a 2nd opinion on a circuit analysis answer

  • Engineering
  • Thread starter Number2Pencil
  • Start date
1. Homework Statement
Use superposition to find [tex]I_L[/tex]

superposition.jpg


2. Homework Equations
-The overall current is the sum of the currents supplied by each source individually


3. The Attempt at a Solution

for source B only (current source is open):

---ohm's law: [tex]\frac{100V}{15k + j25k} = 3.43mA( -59.04 degrees)[/tex]

Here is where I'm having to defend my answer:

for souce A only (voltage source shorted):

---since there is no phase shift labeled, it should be assumed that the current source can be treated as a DC source, treating the inductor as a short, making [tex]I_L[/tex] -20mA

Is this wrong? Should I treat a current source as AC if it has other AC sources involved in the circuit? If this is so I'd just do a current divider to get [tex]I_L[/tex]
 

Answers and Replies

161
0
I believe the question would have to be more explicit in defining whether the 20mA is an ac or dc source.
 
Well no extra information was given than what's shown, yet I got it marked wrong for treating it one way over the other...

Am I going to have to call out my professor again? I'm losing all my brownie points because of his dud test questions
 
Gokul43201
Staff Emeritus
Science Advisor
Gold Member
6,987
14
I would imagine the "+" by the current source tells you it's a dc source.
 
Well actually he graded it as it being an AC source.
 
161
0
If you are answering the question as part of a test and if the professor is not available to clarify, then I guess you could always offer both solutions, one for each case.

Failing that, then I suppose at the last resort you should treat it as ac since, as you said, there are other ac sources in the circuit.
 
161
0
I would imagine the "+" by the current source tells you it's a dc source.
Hmm... but a "+" sign also appears beside the dependent voltage source and that one is clearly ac.
 
Gokul43201
Staff Emeritus
Science Advisor
Gold Member
6,987
14
Hmm... but a "+" sign also appears beside the dependent voltage source and that one is clearly ac.
Haha! Yes, it does. What on earth is it for, then?
 
161
0
For the dependent voltage source, I would imagine that it is there to indicate where the +terminal is (neccesary in defining voltage). I don't know why it appears beside the current source.
 

Related Threads for: I need a 2nd opinion on a circuit analysis answer

Replies
2
Views
1K
  • Last Post
Replies
1
Views
1K
Replies
6
Views
869
Replies
3
Views
2K
Replies
10
Views
1K
Replies
8
Views
5K
  • Last Post
Replies
3
Views
456
Top