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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In pure capacitor circuit, average power is
0
1
∞
1.414
0
Quick Summary: In an ideal (pure) capacitor, the current leads the voltage by a phase angle of $90^\circ$ (or $\pi/2$ radians). Since the average power consumed in an AC circuit is defined by the product of RMS voltage, RMS current, and the power factor (cosine of the phase angle), the average power becomes zero because $\cos(90^\circ) = 0$.
In an ideal (pure) capacitor, the current leads the voltage by a phase angle of 90° (or π/2 radians). Since the average power consumed in an AC circuit is defined by the product of RMS voltage, RMS current, and the power factor (cosine of the phase angle), the average power becomes zero because cos(90°)=0.
P=VrmsIrmscos(ϕ) — General expression for average power in AC circuits
ϕ=90° — Phase angle between voltage and current in a pure capacitor
In a purely capacitive circuit, the capacitor stores energy in its electric field during one quarter of the cycle and returns it to the source during the next quarter. As there is no resistance, no electrical energy is dissipated as heat. Consequently, the net energy exchange over a complete cycle is zero, resulting in zero average power consumption.
A pure capacitor is a non-dissipative component (reactive element).
Power factor (cosϕ) of a pure capacitor is zero.
The component stores and releases energy but does not consume it.
The instantaneous power fluctuates, but the net average over one cycle is zero.
Used for power factor correction in inductive circuits.
High efficiency as there is no power loss due to heating.
Cannot perform work that requires energy dissipation (e.g., heating).
In real-world scenarios, capacitors have Equivalent Series Resistance (ESR) which leads to small power losses.
Power factor improvement in industrial networks.
DC blocking and AC coupling in electronic circuits.
In practical capacitors, the power loss is non-zero due to the dielectric loss and the resistance of the plates/leads, represented by ESR.
Option B (1) would imply a resistive circuit at unity power factor, while option D (1.414) is related to the peak-to-RMS ratio of a sine wave (sqrt2).
A is correct — The average power in a purely capacitive circuit is zero because the current leads the voltage by 90°, resulting in a power factor of zero.
Always remember that pure inductors and pure capacitors are purely reactive components that consume zero average power; only resistors dissipate real power.