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rtareen
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- TL;DR Summary
- The voltages across all components at any instant is equal to the voltage of the source at that instant. But we vectorially add the amplitudes of each component to find the source amplitude. Also, the source voltage is usually out of phase with the source current. We get the phase angle from the phasor diagram, but it doesn't make intuitive sense that the source voltage and source current are out of phase.
Attached is the section from the book. I am doing section 31.3
We know that an AC source gives a sinusoidal varying current, and as far as I know its always given by ##i(t) = Icos(wt)##. Its like we take the current to be the base of all other quantities, so we use it to derive everything else. But nothing was explained as to how this current is generated by the AC source. I know one way where we can alternate the current by the rotating a conducting loop with a dc source in a magnetic field, but I doubt that's what this is. Just out of curiosity, would we be able to configure the exact same kind of LRC circuit described in this section using the rotating loop configuration?
Next we try to find a function for the ac source voltage as a function of time. But to do this we need the amplitude. Can somebody explain why we have to use phasors to find the amplitude?
Also, for equation 31.21, will this work to find the impedance if we have more than one resistor, or more than one inductor? I don't even want to think about what will happen if we have more than one capacitor.
Anyways, once we know the current amplitude and the impedance we have the ac source voltage amplitude ##V##. So now we need to find the function for it. I assume we are using the cosine function because earlier in the chapter we defined the instantaneous current, resistor voltage, inductor voltage, and capaitor voltage to the projection of their phasors onto the horizontal axis. We can use the phasor diagram to solve for the phase angle. But why are the current, and voltage, which come from the same source, not in phase? What is the explanation?
We know that an AC source gives a sinusoidal varying current, and as far as I know its always given by ##i(t) = Icos(wt)##. Its like we take the current to be the base of all other quantities, so we use it to derive everything else. But nothing was explained as to how this current is generated by the AC source. I know one way where we can alternate the current by the rotating a conducting loop with a dc source in a magnetic field, but I doubt that's what this is. Just out of curiosity, would we be able to configure the exact same kind of LRC circuit described in this section using the rotating loop configuration?
Next we try to find a function for the ac source voltage as a function of time. But to do this we need the amplitude. Can somebody explain why we have to use phasors to find the amplitude?
Also, for equation 31.21, will this work to find the impedance if we have more than one resistor, or more than one inductor? I don't even want to think about what will happen if we have more than one capacitor.
Anyways, once we know the current amplitude and the impedance we have the ac source voltage amplitude ##V##. So now we need to find the function for it. I assume we are using the cosine function because earlier in the chapter we defined the instantaneous current, resistor voltage, inductor voltage, and capaitor voltage to the projection of their phasors onto the horizontal axis. We can use the phasor diagram to solve for the phase angle. But why are the current, and voltage, which come from the same source, not in phase? What is the explanation?
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