Phasor Diagram of Capacitor in AC Circuit
Introduction
In an AC circuit, a capacitor is a crucial component that stores energy in the form of an electric field. To analyze the behavior of a capacitor in an AC circuit, we need to understand the concept of phasors and how to draw phasor diagrams. In this article, we will explore the phasor diagram of a capacitor in an AC circuit.
What is a Phasor Diagram?
A phasor diagram is a graphical representation of the voltage and current of an AC circuit. It is a powerful tool used to analyze and design AC circuits. A phasor diagram consists of a set of vectors that represent the voltage and current of the circuit, with the xaxis representing the real part and the yaxis representing the imaginary part.
Phasor Diagram of a Capacitor
The phasor diagram of a capacitor in an AC circuit is shown below:
Capacitive Reactance (XC)
The capacitive reactance (XC) is the opposition to the flow of current in a capacitor. It is represented by a vector that is perpendicular to the voltage vector. The angle between the voltage vector and the capacitive reactance vector is 90 degrees, leading the voltage vector.
Current Phasor (I)
The current phasor (I) is the representation of the current flowing through the capacitor. It is also represented by a vector that is perpendicular to the voltage vector. However, the current phasor lags the voltage phasor by 90 degrees.
How to Draw a Phasor Diagram of a Capacitor
To draw a phasor diagram of a capacitor, follow these steps:
 Draw the voltage phasor (V): Draw a vector to represent the voltage across the capacitor. The length of the vector represents the magnitude of the voltage.
 Draw the capacitive reactance phasor (XC): Draw a vector perpendicular to the voltage phasor, leading the voltage phasor by 90 degrees.
 Draw the current phasor (I): Draw a vector perpendicular to the voltage phasor, lagging the voltage phasor by 90 degrees.
Example Phasor Diagram of a Capacitor
Consider a capacitor with a capacitance of 10 μF connected to an AC voltage source with a frequency of 50 Hz and a magnitude of 12 V. The phasor diagram of this circuit is shown below:
Phasor Diagram:
V (12V, 0°)


XC (j159.15Ω, 90°)


I (0.75A, 90°)
In this example, the voltage phasor is 12 V, the capacitive reactance phasor is j159.15Ω, and the current phasor is 0.75 A.
Conclusion
In conclusion, the phasor diagram of a capacitor in an AC circuit is a powerful tool used to analyze and design AC circuits. By understanding the capacitive reactance and the current phasor, we can determine the behavior of the capacitor in the circuit. By following the steps outlined above, you can easily draw a phasor diagram of a capacitor and analyze the circuit.