NCERT Solutions for Class 12 Physics Chapter 7 – Alternating Current

NCERT Solutions for Class 12 Physics Chapter 7 – Alternative Current contain all the core concepts that have been covered in the chapter. These NCERT Solutions assist you in ensuring your thorough preparations for your Class 12 exams. The chapter includes various fundamentals which are directly and indirectly used in solving all the questions present in the chapter. Topics like impedance of coil, peak voltage, RMS voltage, time lag, RC circuit etc. have been dealt with in the chapter.

CBSE Class 12 Physics NCERT Chapter 7 – Alternative Current comprises a total of one exercise and 26 diverse questions. All of these questions are based on the fundamentals of the chapter and along with their theory explanations, mathematical representation and formulas. The chapter has numerical problems, reasoning questions, descriptive derivations and simple formula based problems.

The NCERT Solutions for Class 12 Physics Chapter 7 – Alternative Current by Instasolv, is an effort to provide a simple and student-friendly learning environment. Once you start engaging with these solutions, you will develop a firm command on the subject matter and the major concepts which require a good deal of understanding. At Instasolv, we aim at ensuring a productive, stress-free and fruitful way of studying and scoring well in your Class 12 CBSE board exams.

Important Topics for NCERT Solutions for Class 12 Physics Chapter 7 – Alternative Current

Alternating Current 

As the name of the chapter makes it clear, here you will learn about Alternating Current which is known as AC. The very simple example of AC would be the electric mains supply which is received in our houses. These currents have a voltage which varies with the sine function with time, therefore the voltage is also termed as an alternating voltage. 

Alternating Current Voltage is more versatile than the Direct Current Voltages and that is the reason why it is preferred over DC current. It is used in most of the electronic devices which are used by us because it can easily be converted from one voltage to another by the use of a transformer. 

Alternating Current Voltage applied to an Inductor and a Capacitor

This chapter will introduce you to various applications of the Alternating Current Voltage and their mathematical representation, working, formula, diagram and derivation. The chapter deals with AC applied to an inductor and the AC applied to a capacitor. This includes various fundamentals like magnetization, demagnetization and Kirchhoff’s law. Alternating current applied to a series LCR Circuit has also been dealt with in the chapter. 


Systems which have oscillating tendencies on a particular frequency have resonance as their virtue. It is also described as a characteristic of the RLC Series. Resonance can also be explained as the natural frequency of a system. In a condition when the frequency of a system is resonant, the current amplitude of that very system is maximum. 


This is one of the very essential concepts that are dealt with in the chapter. This topic will fetch you a lot of marks in your exams. Transformers are used to change the alternating voltage of current from one value to another. Depending on the change from higher to smaller or from smaller to higher, there are two kinds of transformers. You will also learn terms like flux leakage, the resistance of winding, hysteresis, eddy currents etc. under this topic. 

Exercise-Wise Discussion of NCERT Solutions for Class 12 Chapter 7- Alternative Current

  • The exercise begins with a very simple and basic question where you are given the voltage and current of the resistor and you are required to find the RMS value of the current that is flowing through the circuit and the net power that is consumed by the entire cycle. There are other such simple questions like question 7.4 and question 7.5. 
  • In question 7.9 you will be given the values of variable frequency, current of an LCR Circuit and you are required to find the average power transmission of the same. There are more such formula based questions in the chapter where you are required to just place the correct values in the equation and you will get the answer to the problem. Such questions easily fetch marks and are important from the CBSE exam perspective.
  • Further, in question 7.13, you will come across inductance and its value, here you will be asked to time lag and the maximum current of the coil. 
  • Question 7.16 is a continuation from the previous question and you are required to find the time lag. Here you will have to invest your analytical skills while deriving the answer. In the end, you also have to explain why a capacitor is also considered to be a conductor with a very high frequency and then present a comparison of this and the capacitor of a direct current after its steady state. 
  • Overall the questions will prepare you to use all the information and knowledge you have gained from the chapter and channelize it to get good marks and perform well in your board examinations. 

Benefits of NCERT Solutions for Class 12 Physics Chapter 7 – Alternative Current

Instasolv’s team of expert and experienced professionals have left no stone unturned in covering each and every question from the chapter. All the NCERT solutions have been organized in a step by step manner for your independent learning. The solutions have been formulated in accordance with the latest CBSE Syllabus. The most remarkable fact about Instasolv’s NCERT Solutions for Class 12 Physics Chapter – ‘Alternative Current’, is that they are free of cost.