quick question about picking the reference

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kougou

Joined Oct 20, 2012
8
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?
 

davebee

Joined Oct 22, 2008
540
Yes. Everything is relative to "common", including phase shift.
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.
 

#12

Joined Nov 30, 2010
18,224
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.
 
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