I am to draw an impedance diagram of a low pass filter comprising resistor &
capacitor, and to indicate the phase angle. I am in dispute with teacher on
the phase angle.
Is the phase angle found by:
1) -arctan(wRC)
or
2) -arctan(Xc/R)
Appreciate if someone could advise which one of the above is correct.

TIA

On Sat, 11 Nov 2006 05:46:06 -0000, "BIGEYE"
wrote:

I am to draw an impedance diagram of a low pass filter comprising resistor &
capacitor, and to indicate the phase angle. I am in dispute with teacher on
the phase angle.
Is the phase angle found by:
1) -arctan(wRC)
or
2) -arctan(Xc/R)
Appreciate if someone could advise which one of the above is correct.

TIA


#1 gets the nod. Which did you pick?
http://www.phys.unsw.edu.au/~jw/RCfilters.html

"BIGEYE"

I am to draw an impedance diagram of a low pass filter comprising resistor
& capacitor, and to indicate the phase angle. I am in dispute with teacher
on the phase angle.
Is the phase angle found by:
1) -arctan(wRC)
or
2) -arctan(Xc/R)
Appreciate if someone could advise which one of the above is correct.


** Xc = 1/ wC

so Xc/R = 1/ wRC

and R/Xc = wRC


When C is small, Xc is large and in case of a LPF the phase angle ( or phase
shift ) approaches zero when C is small.

Only formula 1 give zero phase for small C.




....... Phil

Thanks for that, teach is right! I picked #2
"Ross Herbert" wrote in message
news
On Sat, 11 Nov 2006 05:46:06 -0000, "BIGEYE"
wrote:

I am to draw an impedance diagram of a low pass filter comprising resistor
&
capacitor, and to indicate the phase angle. I am in dispute with teacher
on
the phase angle.
Is the phase angle found by:
1) -arctan(wRC)
or
2) -arctan(Xc/R)
Appreciate if someone could advise which one of the above is correct.

TIA


#1 gets the nod. Which did you pick?
http://www.phys.unsw.edu.au/~jw/RCfilters.html

BIGEYE wrote:
Thanks for that, teach is right! I picked #2

that is just general current in the circuit.