# Homework Help: Circuit analyse -- LR circuit frequency response

1. Nov 14, 2016

### 8700

1. The problem statement, all variables and given/known data

Find X

2. Relevant equations

V1(t)=8cos(12000t)
V0(t)=Xcos(12000t+θ)

3. The attempt at a solution

I've tried quiet alot actually, but all in vain. Seems like I am either misunderstanding something, or i am just too tired to think at the moment. Either way, I am frustated!

Last edited by a moderator: Nov 14, 2016
2. Nov 14, 2016

### Staff: Mentor

What technique would you expect to use for this type of problem? If the inductor were replaced with a resistor, what would your answer be?

Have you worked with Phasors? What about Differential Equations? You will probably use one of those techniques to solve this, depending on what you have been learning in class...

3. Nov 14, 2016

### 8700

we have mostly been working with phasors, which is those tools i am using.

I know that the following.

v(t)=Re{Vejωt}=VAcos(ωt+Φ)

and

V=VAe=VA∠Φ

somehow I can't seem to get further then this.

I am considering to use the transfer function, and use that to solve for X

Last edited: Nov 14, 2016
4. Nov 14, 2016

### Staff: Mentor

If the inductor were replaced with a resistor, what technique would you use?

And with the inductor put back in place, how can you use phasor impedances to do a similar calculation?

5. Nov 14, 2016

### 8700

Hmm I would probably use the voltage divider

Could I not do that with the transfor function?

6. Nov 14, 2016

### Staff: Mentor

7. Nov 14, 2016

### 8700

I take that as an yes :D

8. Nov 14, 2016

### Staff: Mentor

Yep. And if you want to see some good examples of how to work with them, just do a Google Images search on Phasor Voltage Divider...