Power is equivalent to the product of voltage and time. In an AC circuit, Electromotive force and current can constantly change with respect to time; this is the primary cause we can’t determine its power. An AC circuit’s instantaneous power can be estimated to yield the circuit’s average power; when an AC circuit includes a resistor, the power may increase. When a capacitor is connected in series to a resistor, the alternating current circuit’s power may decrease. An AC circuit’s average power is called the electrical circuit’s true power.
The alternating current or AC circuit’s power factor is the ratio of actual power dissipation to apparent power dissipation in the circuit.
cos Ï• = R/Z
The power of an alternating current circuit varies between 0 and 1. It is 0 for inductive or capacitive circuits and 1 for purely resistive circuits.
Important Questions with Answers
1. What is the power factor?
The power factor is defined as the cosine of the angle between voltage and current.
2. Give three examples where alternating current is used.
Most electrical products, including fans, light bulbs, air conditioners, and motors, use alternating current (AC).
3. What is the operating principle of AC generators?
According to Faraday’s law of electromagnetic induction, the electromotive force that is voltage or emf is induced in a current-carrying wire that cuts a uniform magnetic field, which serves as the foundation for AC generators.
4. What is the true power formula?
The actual or true power is calculated in watts and represents the power lost due to the circuit’s resistance to doing functional work. The real power,
P = VI cos Φ
Where, Φ is the phase difference between the voltage and current phasors, I is the current of the RMS, and V represents the RMS voltage.
5. How do you calculate the power factor of an alternating current circuit?
The power factor is determined as the cosine of the phase difference between voltage and current. It is estimated using the formula,
Power Factor = cos Φ
Where, Φ is the phase difference between the voltage and current phasor.
6. Why is alternating current used instead of direct current?
Alternating current (AC) is much easier and less expensive than direct current (DC). DC step-up/step-down transformers are very complicated. This is why alternating current (AC) is used for power transmission.
7. What is alternating current?
An alternating current, or AC, is a current that varies its polarity and magnitude at regular time intervals. It can also be defined as an electrical current that regularly varies or reverses its direction, unlike the direct current (DC), which constantly flows in a single direction.
8. How is electricity measured?
a. Gram
b. Watts
c. Kilogram
d. Farad
Answer – b. Watts
Explanation – Watts are power units used to measure electricity. A watt is a unit of electrical power equivalent to one ampere at one volt of pressure.
9. What device converts alternating current into direct current?
A rectifier is an electrical device that transforms AC or alternating current to DC or direct current, which flows in just one direction.
10. What is the process by which alternating current is created?
An alternating current is created by switching the voltage between two terminals at a set frequency interval. The potential difference between the positive and negative terminals is measured in volts.
Practice Questions
1. What occurs when an inductor or capacitor is connected to a resistor in an alternating current circuit?
2. When an inductor is connected in series to a resistor, the power of the alternating current circuit diminishes.
- True
- False
3. What is the formula for determining apparent or virtual power?
4. What is an LCR circuit?
5. What is electricity?
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To learn about the difference between ‘Alternating Current and Direct Current’, watch the video below.
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