1
\$\begingroup\$

Usually, phasors are represented by Acos(ωt + φ) where φ is the phase angle. Using this convention, we need to convert sin(ωt) into cos(ωt - 90) to get its phase angle like this thumbnail on a YouTube video.

But in EE, the AC sources are usually sinusoids and back when I first studied about phasors in physics, they were introduced as Asin(ωt + φ) with φ being the phase angle.

What is the correct way to represent sine waves (say 120sin(120πt)) in polar form?

\$\endgroup\$
6
  • 2
    \$\begingroup\$ I don't see that there is a best way; either or one might be more applicable to a particular problem. \$\endgroup\$
    – Andy aka
    Jun 5, 2021 at 10:39
  • \$\begingroup\$ So there is no particular "convention"? \$\endgroup\$
    – Elrond
    Jun 5, 2021 at 10:43
  • \$\begingroup\$ There might be for some applications but you mention no applications. \$\endgroup\$
    – Andy aka
    Jun 5, 2021 at 10:53
  • \$\begingroup\$ Say V = 120sin(120πt) Volts then according to EE convention it should be 120, angle(-90 degrees) ? \$\endgroup\$
    – Elrond
    Jun 5, 2021 at 10:55
  • 1
    \$\begingroup\$ There is no one, common convention. So even in the above comment example, it is ambiguous. To avoid ambiguity, always specify the reference phasor at the beginning itself. \$\endgroup\$
    – AJN
    Jun 5, 2021 at 11:11

1 Answer 1

3
\$\begingroup\$

All that matters is the phase difference. There is no absolute phase angle. It's just like voltage -- it's always measured relative to something you pick as a reference.

But in EE, the AC sources are usually sinusoids and back when I first studied about phasors in Physics, they were introduced as Asin(wt + phi) with phi being the phase angle.

They were just saying that sin(wt+phi) has a phase angle of phi with respect to sin(wt).

It's ok to represent sinusoid waveforms with either sin() or cos(). When speaking of phase angle just pick a a form that represents a phase angle of 0 and stick to it.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.