FAQs
The power factor is the cosine of the angle of the impedance. Since a pure capacitive circuit has no real component of the impedance, then the power factor is 0.
When viewing the sine wave of a purely capacitive circuit, which of the following lags the current? ›
Looking at the graph, the current wave seems to have a “head start” on the voltage wave; the current “leads” the voltage, and the voltage “lags” behind the current. Voltage lags current by 90° in a pure capacitive circuit.
Is 100 of the apparent power used or consumed in a purely resistive circuit? ›
Therefore, it is true that 100% of the apparent power is used or consumed in a purely resistive circuit. This is not the case in circuits that have reactive elements, such as inductors and capacitors, where the current and voltage are out of phase with each other.
What is the opposition to current flow in an AC circuit caused by an inductor called? ›
This opposition to current change is called inductive reactance (X) and is measured in ohms. Unlike resistance, the inductive ohmic value of the coil is dependent on the value of the inductor and how fast the current is changing (2лf for a sine wave).
What is the formula for power factor? ›
PF = kW / kVA
A steel stamping operation runs at 100 kW (Working Power) and the Apparent Power meter records 125 kVA. To find the PF, divide 100 kW by 125 kVA to yield a PF of 80%. This means that only 80% of the incoming current does useful work and 20% is wasted through heating up the conductors.
What does it mean when the power factor is 1? ›
The power factor is the ratio between Real Power and Apparent Power. It's expressed as a value between -1 and 1 and can be either inductive (lagging) or capacitive (leading). If the power factor is 1, then all of the power supplied is being used for productive work and this is called 'unity'.
What is the power factor of a purely resistive load in a three-phase AC circuit? ›
Power Factor Values
For the purely resistive circuit, the power factor is 1 (perfect), because the reactive power equals zero. Here, the power triangle would look like a horizontal line, because the opposite (reactive power) side would have zero length.
What is the formula for capacitance in an AC circuit? ›
Capacitance is measured in Farad (F) and is given by the formula: C = Q/V. A higher value means the capacitor is able to store more electric charges when a voltage is applied. Capacitance is a value that electronics designers pay attention to in both DC and AC circuits.
What is the relationship of current and voltage in a purely capacitive circuit? ›
The phase relationship between current and voltage in a pure capacitive circuit is that the current leads the voltage by 90 degrees. This relationship can be understood through the mnemonic 'ELI the ICE man', where the voltage leads in an inductive circuit (ELI), but the current leads in a capacitive one (ICE).
What is the phase angle in a purely inductive circuit? ›
In a purely inductive circuit, the phase relationship between the current and voltage is such that the current lags behind the voltage by 90 degrees. This means that the current waveform reaches its maximum value 1/4 of a cycle (or 90 degrees) after the voltage waveform reaches its maximum value.
This “phantom power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q.
What is the formula for active power reactive power apparent power? ›
We thus define: Apparent power: S = V x I (kVA) Active power: P = V x Ia (kW) Reactive power: Q = V x Ir (kvar)
Why is AC blocked by inductor? ›
Finally, we say that inductors in series 'block' AC because their reactance oppose changes in current. The higher the AC frequency (bigger dI in dI/dt), the higher the reactance, the more they block.
What is the symbol for reactance? ›
The symbol for reactance is X. To specify a specific type of reactance, a subscript is used. In this case, since it's capacitive reactance, the subscript C is used. The constant 2π comes from the number of radians in one cycle of a sinusoidal ac waveform.
How many electrical degrees are in an AC waveform? ›
The period of a wave in degrees is always 360, but the amount of time one period occupies depends on the rate voltage oscillates back and forth.
What is the power factor of a capacitive circuit always? ›
In a purely capacitive circuit, the current leads the voltage by 90° and the power factor is zero leading.
What is the power in a purely capacitive circuit? ›
Assertion (A) : In purely capacitive AC circuit, average power consumed is zero. Reason (R) : The phase difference between the current and voltage in case of a purely capacitive circuit is 90∘.
What is the percentage of power factor? ›
PF expresses the ratio of true power used in a circuit to the apparent power delivered to the circuit. A 96% power factor demonstrates more efficiency than a 75% power factor. PF below 95% is considered inefficient in many regions.
What is the value of the power factor for a purely resistive circuit? ›
For the purely resistive circuit, the power factor is 1 (perfect), because the reactive power equals zero. Here, the power triangle would look like a horizontal line, because the opposite (reactive power) side would have zero length.