NCERT Solutions for Class 12 Physics Chapter 4 – Moving Charges and Magnetism

NCERT Solutions for Class 12 Physics Chapter 4 – Moving Charges and Magnetism have been formulated to ensure that you are well prepared for your exams. These NCERT Solutions tackle all the major concepts from the chapter. These solutions ensure that you are well-versed with the topics along with a thorough practice and revision of the questions included in the chapter. The chapter will introduce you to topics like torque, uniform magnetic field, the magnitude of the magnetic field, specific charge etc.  

Chapter 4 – Moving Charges and Magnetism consists of one exercise and twenty-eight questions in total. The chapter has a great variety of questions which revolve around the basics that have been dealt in the chapter, including the theory, graphs, charts, diagrammatic explanations, numerical problems and examples. The exercise for Chapter 4 – Moving Charges and Magnetism, consists of short answer questions, observational questions, analytical questions, simple formula based problems, and derivation based questions and numerical problems. 

The NCERT Solutions for Chapter 4 – Moving Charges and Magnetism by Instasolv, is an effort to provide a simplified 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.

Important Topics covered in NCERT Solutions for Chapter 4 – Moving Charges and Magnetism

Lorentz Force 

In this chapter of NCERT Solutions for Class 12 Physics, you will learn about the concept of the Lorentz Force. The force which acts on an electric charge q, due to both of the electric and the magnetic field is written as 

F = q [ E (r) + v x B (r)] ≡ F electric + F magnetic 

And this force is termed to be the Lorentz force. The features of this force discussed in the chapter are –

This force depends on q, v and B. the force on a negative charge is opposite to the force on a positive charge.

The magnetic force q [ v x B ] includes a vector product of the velocity and the magnetic field. The force acts in a sideways direction i.e. it acts in a perpendicular direction to both the magnetic field and the velocity.

In case if the charge is not in motion, the magnetic force becomes null. 


A machine that is used to accelerate the charging of particles or ions at very high energy is known as a Cyclotron. A cyclotron uses both the electric field and the magnetic field in a combination to increase the energy of charged particles. These fields are perpendicular to one another and are therefore known as cross fields. In this chapter, you will study the cyclotron in a detailed manner along with its diagram, formula, and mechanism and theory explanations. 

Ampere’s Circuital Law and the Biot Savart Law

These two laws have been discussed in the chapter in a very detailed manner and there are numerous questions based on the two. These laws are connected to each other. The Ampere Circuit Law has actually been derived from the Biot Savart Law and both of them share a relationship which will be dealt in the chapter. You will come across the mechanism, background and formulas associated with both of these laws, in the chapter. 

Exercise Discussion of NCERT Solutions for Class 12 Chapter 4 – Moving Charges and Magnetism

  • The entire chapter of NCERT Solutions for Class 12 Physics contains one exercise and twenty-eight questions in total. All of these questions aim at testing your observational and analytical skills. They revolve around the major concepts and the fundamentals that have been tackled in the chapter. 
  • The first exercise begins with a very simple numerical where you are given the radius of a circular coil along with its number of turns and the current it carries. You are required to find the magnitude of the magnetic field which is located at the centre of the coil. Here you are required to just write down the formula of the electric field and put values in it. 
  • Question 4.2 and 4.3 are also similar and work on the same principle and formula where you need to figure out the magnitude of the electric field according to the conditions that are given in the question. 
  • The exercise also comprises lengthy questions, as question number 4.10, where you are given all the basic values of two moving coil meters and you are required to find out the ratio of their current sensitivity and their voltage sensitivity. This might appear to be a tricky question but it is an easy solution if you are well versed with the ideas that have been introduced in the chapter and pay attention to each and every step of your solution. 
  • The chapter also has theory-based questions, like question number 4.18 where you have to analyze and observe the conditions that have been given in the question and then present your understanding of the same. 
  • There diagram based questions like 4.24 where you are given six different diagrams and you have to find the force in each of the cases along with the torque on the loop. 
  • Overall the exercise is a very engaging and interesting way of preparing your chapter and brushing up all your skills with constant practise and revision through these questions. 

Benefits of CBSE NCERT Class 12 Physics Chapter 4 – Moving Charges and Magnetism

Our expert team at Instasolv has made sure that all the solutions are presented in a simple and student-friendly manner. We ensure that you build up a solid understanding of the chapter and all its core concepts. Each and every question has been tackled by our team in a stepwise manner and a well-organized explanation. All the answers are in our NCERT Solutions for Class 12 Physics Chapter 4 Moving Charges, follow the latest CBSE Syllabus.