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Important Questions for Class 12 Physics Chapter 7 Alternating Current - Introduction - PDF Download

Class 12

Important questions for Class 12 Physics Chapter 7 are available on our website in a downloadable PDF format. The candidates can practice these important questions to gain more knowledge and get more marks in their board exam. Practising and solving important questions for Class 12 Physics Chapter 7 helps students score good marks in the examinations and overcome their exam fear. 

So, students must download the PDF and start solving these questions. On this platform you will get  free NCERT solutions for chp 7 and other study materials for students.

Before we go through the alternating current important questions PDF, let take  a look at some key points of Class 12 Physics Chapter 7.

  • In Chapter 7 alternating current, we studied about the behavior of alternating current and how the direction of alternating current changes periodically.

  • In Class 12 Physics Chapter 7, we studied how to calculate the RMS value of a given AC and Voltage.

  • We learned how to calculate the average power rating in any circuit given.

  • We come across concepts like electrical components such as capacitors, inductors, and resistors, followed by studying their combinations which are series and parallel combinations.

  • Class 12 chapter 7 of class 12 physics has many interesting topics like AC circuits consisting of only resistors, AC circuits consisting of only inductors, and AC circuits with Capacitance only.

  • In this chapter, we will learn about LCR circuits in series and parallel combinations. We will also learn how to determine the impedance, phase angle, etc.

  • This chapter 7  includes some applications of the topics covered in the unit which is AC dynamos, Transformers, LC Oscillators, etc.

These key points must be remembered before starting the preparation of Class 12 Physics Chapter 7 important questions. To improve their knowledge and learn how to attempt questions from Chapter 7 of Class 12 physics, students are advised to download the PDF available on the eSaral website. 

Important Topics & Sub-topics of Alternating Current Class 12 Physics

Here, on this website we can provide important questions and its solution in pdf format for class 12 chp 7 Alternating Current. Please note that the topics mentioned may vary depending on your curriculum and textbook, the table is being created based upon a sample question paper discussed internally in the coaching center. 

Introduction to Alternating Current

  • Definition of AC and comparison with DC

  • Representation of AC waveform

AC Voltage and Current

  • Peak, peak-to-peak, and RMS values

  • Phasor representation of AC voltage and current

  • Phase difference between voltage and current

AC Circuits with Resistors

  • Ohm's law in AC circuits

  • Impedance and its calculation in resistive AC circuits

  • Power in AC circuits

AC Circuits with Capacitors and Inductors

  • Reactance of capacitors and inductors

  • Impedance of capacitive and inductive AC circuits

  • Phase relationships in RC and RL circuits

  • Resonance in LC circuits

Series and Parallel AC Circuits

  • Analysis of series AC circuits

  • Analysis of parallel AC circuits

  • Power factor and power factor correction

LCR Circuits

  • Analysis of series LCR circuits

  • Resonance in LCR circuits

  • Quality factor (Q-factor) and bandwidth


  • Principle of operation of transformers

  • Transformer equation and turns ratio

  • Ideal transformer and its efficiency

AC Generators

  • Working principle of AC generators

  • Alternators and their construction

Electrical Instruments

  • Moving coil galvanometer

  • Ammeter and voltmeter

Alternating Current Applications:

  • Transmission and distribution of AC power

  • Use of transformers in power transmission

These topics and sub-topics cover the fundamentals of alternating current in Class 12 Physics. Make sure to study each of these in detail and practice solving problems to gain a thorough understanding.

Class 12 Physics Chapter 7 Alternating Current Weightage

The weightage of Chapter 7, "Alternating Current," in the Class 12 Physics curriculum can vary slightly from one educational board to another. However, in most cases, this chapter carries moderate to significant weightage in the overall examination. On average, you can expect it to cover around 8% to 12% of the total marks in the Physics board exam.

In 2023 class 12 physics question papers, it contains 2 object questions and 1 numerical question came from this chapter. As this is a very easy chapter and foundation of a class 12 physics subject, you should easily score well. 

Tips to Solve Class 12 Physics Chapter 7 Alternating Current

Solving Class 12 Physics Chapter 7, "Alternating Current," effectively requires a systematic approach and a clear understanding of the concepts. Here are some tips to help you tackle this chapter:

Understand the Basics: Start by understanding the fundamental concepts of alternating current, such as AC vs. DC, AC voltage and current, and phasor representation.

Practice Regularly: Practice Solving Problems Regularly AC circuits involve mathematical calculations, so practice is crucial to improve your problem-solving skills.

Learn Phasor Diagrams: Master the art of drawing and interpreting phasor diagrams. They are essential for understanding phase differences and impedance.

Focus on Impedance: Understand impedance in AC circuits. It's analogous to resistance in DC circuits but takes into account both resistance and reactance (capacitive and inductive).

Series and Parallel AC Circuits: Practice solving problems related to series and parallel AC circuits. Understand the formulas for impedance and apply them correctly.

Power in AC Circuits: Study how power is calculated in AC circuits. Be aware of the concepts of apparent power, active power (real power), and reactive power.

LRC Circuits and Resonance: Pay special attention to LRC (LR and LC) circuits and their resonance characteristics. Understand how to calculate resonant frequency and bandwidth.

Transformers and Alternators: Study the principles and working of transformers and alternators. Learn the transformer equation and how to calculate turns ratio.

Solve Previous Year Questions: Solve previous year's board exam questions and practice papers to get a sense of the types of questions that can be asked.

Create Summary Notes: Summarize key concepts, formulas, and important points in your own words. This can help in quick revisions.

Practice Time Management: During the actual exam, manage your time wisely. Allocate a specific amount of time to each question and don't get stuck on a single problem.

Stay Relaxed and Confident: Maintain a positive attitude and stay confident during the exam. Avoid last-minute cramming and get a good night's sleep before the exam day.

Benefits of Solving Class 12 Physics Chapter 7 Important Questions with Answers

Solving Class 12 Physics Chapter 7 Important Questions with Answers can offer several benefits

Conceptual Understanding: These questions often cover key concepts, helping you grasp the subject matter more thoroughly.

Exam Preparation: Practicing important questions can improve your exam readiness by focusing on crucial topics.

Time Management: It helps you manage your time effectively during exams by identifying areas where you need more practice.

Performance Improvement: Consistent practice with these questions can lead to better academic performance.

Self-Assessment: You can assess your progress and areas that require further attention.

Preparation for Competitive Exams: If you plan to take competitive exams, these questions can be valuable for preparation.

Remember to complement this practice with a thorough understanding of the underlying concepts and regular study.

Frequently Asked Questions

Question 1: What is the fundamental difference between Alternating Current (AC) and Direct Current (DC)?

Answer: Electric current flows in two ways either in alternating current (AC) or direct current (DC). The main difference between AC and DC is the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, while electrons keep switching directions, going forward and then backwards in AC and making a wave form.



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