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# NCERT Solutions for Class 12 Physics Chapter - 7 Alternating Current - PDF Download

The NCERT Solutions for Class 12 Physics Chapter 7 Alternating Current is solved here to help you in understanding the concepts thoroughly. Chapter 7 Alternating Current of NCERT Solutions for Class 12 Physics gives answers to the questions asked in the textbook. These solutions are solved by our subject expert teachers according to the latest Syllabus.

For the students of Class 12, who are preparing for their Class 12 Board exams and different entrance exams, like JEE and NEET, it is important to have a thorough knowledge of this chapter. Further, you can save your time for revision by studying the NCERT Solutions for Class 12 Physics Chapter 7 Alternating Current . The solutions in PDF can be downloaded for from this website.

## Topics Covered in NCERT Class 12 Physics Chapter 7 Alternating Current

NCERT Class 12 Physics Chapter 7 Alternating Current covers a total of 8 topics. Following are the topics mentioned in chapter 7:

1. Introduction

2. AC Voltage Applied to a Resistor

3. Representation of AC Current and Voltage by Rotating Vectors – Phasors

4. AC Voltage Applied to an Inductor

5. AC Voltage Applied to a Capacitor

6. AC Voltage Applied to a Series LCR Circuit

1. Phasor-diagram Solution

2. Analytical Solution

3. Resonance

7. Power In AC Circuit: The Power Factor

8. Transformers

### Introduction

The direct currents do not change direction with time but voltages and currents that vary with time. The electric mains supply in our offices and homes is a voltage that varies like a sine function with time. Such a voltage is known as alternating voltage or ac voltage and the current driven by it in a circuit is called the alternating current or ac current. Nowadays, most of the electrical devices we use require ac voltage. This is because most of the electrical energy sold by power companies is transmitted and distributed as alternating current.

### AC Voltage Applied to a Resistor

In this topic, you will learn about an electric circuit, where an AC voltage is applied across a resistor. Before applying AC voltage across the resistor, you should know what an alternating current (AC) is. Electric current, which reverses its direction at a regular interval and changes its magnitude continuously with time, is known as an alternating current.

A resistor connected to a source of an ac voltage. Let us consider a source which produces sinusoidally varying potential difference across its terminals. And this potential difference, also called ac voltage.

### Representation of AC Current and Voltage by Rotating Vectors – Phasors

AC voltage and current being sinusoidal in nature can be represented by phasors. A phasor is a mathematical technique to simplify AC circuit analysis and it is a rotating vector whose length is equal to the maximum value of the sinusoidally varying physical quantity and whose angular speed is numerically equal to the angular frequency of the sinusoidally varying function.

### AC Voltage Applied to an Inductor

AC Voltage Applied to an Inductor implies an AC circuit that consists only of an inductor of inductance L which is connected to an AC source and the voltage in an inductor can be measured as the amount of electromotive force (EMF) generated for the change of current.

### AC Voltage Applied to a Capacitor

In the case of an AC voltage, we have an alternating voltage which continuously charges and then discharges the capacitor, when an alternating voltage is applied across a capacitor, the current leads the voltage by a phase angle of 90 degrees. While charging the capacitor the voltage across the plates of the capacitor rises and the charge also increase, and when the voltage across the plates decreases the charge will also decrease.

### AC Voltage Applied to a Series LCR Circuit

In this topic, you will study a series combination of a Resistor, an Inductor and a Capacitor also known as the Series LCR circuit. You will study the growth of the current and some other quantities in this circuit. These circuits are the basic components of many important devices.

### Power In AC Circuit: The Power Factor

Power Factor of an alternating current circuit is the ratio of true power dissipation to the apparent power dissipation in the circuit.

### Transformers

A transformer is a simple device that transfers electric energy from one alternating-current circuit to one or more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage and a transformer works on the principle of electromagnetic induction to step up or step down voltage.

## Some key points of Class 12 Physics Alternating Current are given below

• When a value is given for AC voltage or current, it is called ordinarily RMS value.

• The power rating of an element used in AC circuits known as to its average power rating.

• There are no power losses related with pure capacitances and pure inductances in an AC circuit.

• The power consumed in an AC circuit can never be negative.

• A step-up transformer changes a low-voltage into a high-voltage.

• In an AC circuit, while adding voltages across various elements, one should take care of their phases properly.

## Key Features of NCERT Solutions for Class 12 Physics Chapter 7

Following are the key features of NCERT solution for class 12 Physics chapter 7

• Solutions are focused in the right manner to help you in quickly finding solutions.

• Step-by-step explanation for all questions given in NCERT textbook.

• All solutions are easy to grasp and learn as they are solved by subject expert teachers to match the curriculum.

• NCERT solutions for Class 12 Physics Chapter 7 help develop strong conceptual basics for students, which is important in the final stages of preparation for board and competitive exams.

## FAQs

Question1. What is Alternating Current?

Answer. An alternating current can be defined as a current that changes its magnitude and polarity periodically. It can also be defined as an electrical current that repeatedly reverses or changes its direction opposite to that of Direct Current or DC, which always flows in a single direction.

Question2. What are the topics under chapter 7 Alternating Current?

Answer. Following are the topics under chapter 7

1. Introduction

2. AC Voltage Applied to a Resistor

3. Representation of AC Current and Voltage by Rotating Vectors – Phasors

4. AC Voltage Applied to an Inductor

5. AC Voltage Applied to a Capacitor

6. AC Voltage Applied to a Series LCR Circuit

1. Phasor-diagram Solution

2. Analytical Solution

3. Resonance

7. Power In AC Circuit: The Power Factor

8. Transformers