Getting the degrees and frequencies.

Discussion in 'Homework Help' started by the_file, Apr 16, 2012.

  1. the_file

    Thread Starter New Member

    Apr 15, 2012
    6
    0
    What are the formulas to get the phase shift and various degrees at certain frequencies for the capacitor if the VAC is at 14V peak. I attached the schematic.

    ALSO what would the formulas be if the capacitor were an inductor.

    I am currently studying AC theory and I am wondering if there is an easy way to do this.

    Thanks in advance.
     
  2. panic mode

    Senior Member

    Oct 10, 2011
    1,321
    304
    you need to derive transfer function and then plot it (separately magnitude and phase - two graphs per function, lookup bode plot).

    Z1=R1
    Z2=1/sC1

    Vo(s)=Vi(s)*Z2/(Z1+Z2)

    and transfer function is H(s)=Vo(s)/Vi(s)=Z2/(Z1+Z2)

    where s=jω
    and ω=2πf

    if it was inductor instead of capacitor then

    Z2=sL
     
  3. WBahn

    Moderator

    Mar 31, 2012
    17,757
    4,800
    First, the schematic leaves a lot to be desired. Voltage is a directed (meaning it has polarity) measurement between two points. If only one point is given, then convention states that the given point is the positive node and 'ground', which is merely some other arbitrary point in the circuit, is the negative node. In this diagram, the polarity of Vout is not indicated and no reference point (ground) is indicated for Vin.

    Sure, I can guess what is intended and am almost certain to be correct. But engineering isn't about guessing, at least not about stuff like this.

    Second, you talk about "phase shift and various degrees" as though they are different things. What do you mean by "various degrees".

    Third, the amplitude of the voltage source has no effect on the phase shifts.

    Fourth, are you looking for help in obtaining the necessary formulas, or do you just need someone to provide them to you?

    Now, where are you at in your AC circuits course? Have you talked about phasors? Have you talked about complex impedance? Have you talked about s-domain representations? Or are you still at the very beginning of the material and are working only in the time domain with the differential equations?
     
  4. jegues

    Well-Known Member

    Sep 13, 2010
    735
    43
    Using phasors would be the simplest way to extract the information you desire about any of the components in the circuit, provided it is considered to be at steady state.
     
  5. the_file

    Thread Starter New Member

    Apr 15, 2012
    6
    0
    I got this problem and figured it out. Thanks everyone who posted it really helped with it. Its a few concepts that I was not understanding but its good.
     
Loading...