quick question about picking the reference

Discussion in 'General Electronics Chat' started by kougou, Sep 23, 2013.

  1. kougou

    Thread Starter New Member

    Oct 20, 2012
    8
    0
    Hi all

    I have a quick question regarding picking the reference for a AC steady state circuit. I know that if we pick a particular node to be our "ground" or reference node, then, every other node voltages are compared against with the "ground".

    I am wondering what about the phase? if we pick that node is the ground (or 0 voltage), do we automatically assume that it has a 0 degree phase?
     
  2. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    Yes. Everything is relative to "common", including phase shift.
     
  3. davebee

    Well-Known Member

    Oct 22, 2008
    539
    46
    Is that right? I would think phase would be undefined for a point of no voltage.

    A phase measurement has to be in reference to the phase of another non-zero part of the circuit (or time, I think).

    Somethng like this is stated partway down this page

    http://www.allaboutcircuits.com/vol_2/chpt_1/5.html

    "Phase shift, like voltage, is always a measurement relative between two things. " and then it refers to other oscillating waveforms.

    But also, I'd assume that phase could be stated relative to absolute time; ie., the phase angle is zero at some specific point in time.
     
  4. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    I think you caught me being wrong.:rolleyes:

    There's no such thing as phase compared to no voltage at all.
    Sorry. Stupid strikes everybody from time to time.
     
    Last edited: Sep 23, 2013
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