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June 10th, 2019, 10:06 AM   #1
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Phasor Representation of sine wave

I don't understand why Sine wave should be represented as a phasor, that is, as a circle with a rotating vector. Why should it be rotating at angular speed (omega)? This is an additional item that confuses me. Suppose in the picture I am assuming it is moving at some speed; if it runs at twice the speed, how does the waveform will look like? I know the questions are not clear, but how I do I link omega, t, frequency?
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 Sine.jpg (12.0 KB, 8 views)

Last edited by skipjack; June 11th, 2019 at 04:28 AM.

 June 11th, 2019, 04:40 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,966 Thanks: 2216 The sine wave doesn't need to be related to a rotating vector. Although the diagram refers to the time domain, the horizontal axis for the sine wave uses ωt, which is dimensionless and corresponds to an angle in the left-hand diagram (if ω isn't zero). The word "frequency" relates to how often something occurs. If you choose to consider a vector that rotates at a constant non-zero rate, it's convenient to draw a horizontal axis that aligns with the vector at time zero. If that alignment occurs n times per second, it would be reasonable to refer to "n times per second" as the frequency of the rotation. After t seconds have elapsed, the vector has rotated through 2$\pi$n radians, so ω = 2$\pi$n. You asked how the waveform looks if the frequency is changed. What the waveform "looks like" depends on the scaling used for drawing it. If the frequency is changed and a corresponding change is made to the scaling, the waveform will look the same. Thanks from topsquark and MathsLearner123
June 11th, 2019, 07:38 AM   #3
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Quote:
 Originally Posted by skipjack After t seconds have elapsed, the vector has rotated through 2$\pi$n radians, so ω = 2$\pi$n.
Will it be 2$\pi$nt?

 Tags phasor, representation, sine, wave

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