Phasor Diagrams in single phase series circuits

In summary, in a single phase series circuit, the current should always be drawn along the x-axis and the voltage should be drawn with respect to it. The common factor should be on the horizontal line and other voltages should be plotted relative to it. The phase of the voltage will vary depending on the component, but the current will remain the same. It is acceptable to use either method, as long as it is consistent and suits the problem at hand.
  • #1
Physicist3
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In single phase series circuits, should the current always be drawn along the x-axis and the voltage then drawn with respect to it? E.g. Should Vr be drawn in line with I, VL leading by 90 degrees (pointing upwards) and Vc lagging by 90 (Pointing down)? The reason I ask is because I've seen some diagrams for a purely capacitive circuit where the voltage is along the x-axis and the current is pointing upwards? but I always thought you drew the diagrams with the common factor on the horizontal?
 
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  • #2
If the sinusoidal voltage is given to you in the form
[tex]v(t)=V_msin({\omega}t+\phi)[/tex]
then when you represent it on the phasor diagram, it has that angle([itex]\phi[/itex]) with respect to the positive, real axis. If all you know is the current leads/lags the voltage, then set one of the phasors as your reference, and the other phasor will either lead or lag that phasor depending on the orientation that you went with. I usually have voltage as my reference, and if the current lags (purely inductive), then the current phasor will be -90 degrees from the reference voltage phasor. If it leads in a purely capacitive network, the opposite is true.
For example, [itex]V_{RMS}e^{j0}[/itex] and [itex]I_{RMS}e^{-j90}[/itex] is the same as [itex]V_{RMS}e^{j90}[/itex] with [itex]I_{RMS}e^{j0}[/itex] because ultimately the phasor is rotating counterclockwise about the origin, at 90 degrees with respect to each other.
 
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  • #3
Thanks for the reply. Is it acceptable to use either method as I've always been taught to work from the principle that current is same everywhere in series circuits and hence should go on the positive real axis.
 
  • #4
Soon enough you'll be ambidestrous, swapping back and forth to whichever convention better suits the problem at hand.

It's just like learning language.
 
  • #5
You would plot voltages on a screen that only showed voltages, not currents.

In a series circuit, if there is a resistor present, the voltage across the resistor will be in phase with the current, so this will be plotted along a horizontal line and other voltages will be plotted relative to this.

The current in all components of a series circuit is the same, but the phase of the voltage will vary depending on the component.
 

FAQ: Phasor Diagrams in single phase series circuits

1. What is a phasor diagram in a single phase series circuit?

A phasor diagram is a graphical representation of the voltage and current in a single phase series circuit. It is used to understand the relationship between these two quantities and to analyze the circuit's behavior.

2. Why are phasor diagrams important in single phase series circuits?

Phasor diagrams are important because they allow us to simplify the analysis of a circuit and make calculations easier. They also provide a visual representation of the circuit's behavior, making it easier to understand and troubleshoot.

3. How do you draw a phasor diagram for a single phase series circuit?

To draw a phasor diagram, you first need to determine the voltage and current values in the circuit using Ohm's law and Kirchhoff's laws. Then, plot the voltage and current on a complex plane, with voltage on the vertical axis and current on the horizontal axis. Finally, draw a line from the origin to the point representing the voltage, and another line from the origin to the point representing the current. These lines are called phasors.

4. What information can be obtained from a phasor diagram in a single phase series circuit?

A phasor diagram provides information about the magnitude and phase difference between voltage and current in a circuit. It can also be used to calculate the circuit's impedance and power factor.

5. How is a phasor diagram useful in solving circuit problems?

A phasor diagram allows us to apply basic trigonometry to calculate the voltage, current, and other circuit parameters. It also helps us visualize the circuit's behavior and understand the impact of changing component values on the overall circuit performance.

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