[Physics Class Notes] on Power in AC Circuit Pdf for Exam

Based on the direction of current flowing through the circuit, it is differentiated in two types. One is Alternating current and another is Direct current. When an electric current reverses its direction periodically while flowing through an electric circuit is called Alternating Current (AC). On the other hand, when current flows in only one direction is known as Direct current (DC).

The major advantage of alternating current is that AC voltages can be easily transformed from higher to lower voltage levels and vice-versa. Due to this virtue, high voltage power from power stations can be reduced to a safer voltage for domestic use. Only Alternating current is compatible with capacitors and inductors. By using them within the Alternating current circuits, the flow of electricity can be turned. This property helps tune the radio stations. Because of these reasons, AC electricity is most preferred for home appliances.

 

Power Consumed in an AC Circuit

An electric circuit produces power which is given by the expression, P= I V.

Where, I – the current flowing through the circuit and

V- Voltage across it.

AC circuits always offer reactance, therefore there are two components of power, a power component because of the magnetic field and another because of the electric field. The average power absorbed by the circuit becomes the sum of power stored and returned through a complete one cycle. Thus, the average power consumed by the circuit will be the instantaneous power within one cycle.

 

Power Factor

• The power factor of an alternating current is defined as the ratio of the true power flowing through the circuit to the apparent power present in the circuit. 

• It is usually in the interval of -1 to 1 and is dimensionless.

Power Factor = [frac{ text {True power}}{text{Apparent power}}]

Also, cosΦ = [frac{R}{Z}]

R- resistance in the circuit

Z- impedance of the circuit.

Definition of Power in AC Circuit

The rate of doing work or the amount of energy transferred by a circuit per unit time is known as power in AC circuits. It is used to calculate the total power required to supply a load. Power factor: In an AC circuit, the power factor (PF) is defined as the ratio of real power (P) to apparent power (S). The PF can be expressed in percent or decimal form.

The Importance of Power in an AC Circuit 

The power in an AC circuit is very important as it determines the amount of current that flows through the circuit and hence, the size of the wire required. The voltage and current waveforms are also affected by the power factor. A low PF means that a lot of energy is being wasted in the form of heat due to poor utilization of electricity. This can cause overheating and failure of electrical equipment.

The Importance of the Power Factor

The power factor is very important as it determines the amount of current that flows through the circuit and hence, the size of the wire required. The voltage and current waveforms are also affected by this factor. A low PF means that a lot of energy is being wasted in the form of heat due to poor utilization of electricity which can cause overheating and failure of electrical equipment.

Here are Some Tips to Study the Power in AC Circuit

1. Knowing how to solve simple AC circuit problems helps you learn more about PF and its applications in real-life situations. Some examples include finding the reactive watts, total watts, current, and voltage for a given power factor. These examples can help you learn more about PF and its applications in real-life situations. Here are some tips to study the Power Factor:

2. Know the basics- It is important to know the basics of an AC circuit before studying the power factor. So that, you can easily understand the importance and applications of the power factor.  Solve simple problems- Knowing how to solve simple AC circuit problems helps you learn more about PF and its applications in real-life situations. Some examples include finding reactive watts, total watts current, or voltage for a given power factor. Learn from textbooks – Textbooks contain detailed information on formulas along with solved examples.

3. Practice more problems- Practicing a lot of examples is one of the most effective ways to learn and understand the concept of the power factor which will help you to use the power factor in real-life problems.

4. Understanding and applying PF concepts is an important part of learning more about electrical equipment and devices that implement it.

5. Studying examples from textbooks along with practicing lots of problems helps one learn quickly as well as understand PF better which ensures correct usage in real-life situations.

6. Appear for mock tests- Mock tests help you understand where you stand with the concept of power factor. Last but not least, appearing for mock tests gives one an idea about how much they have learned about power factors and what all they need to focus on.

7. Learn the rules- It is important to learn the rules of the power factor before solving any problem.

Fun Facts

• Ohm’s law for the RMS value of an alternating current is calculated by dividing the RMS voltage by the impedance.

• The average power delivered to an LCR circuit varies with the phase angle.