NCERT Solutions for Class 12 Physics Chapter 4 – Moving Charges and Magnetism
NCERT Solutions for Class 12 Physics Chapter 4 – Moving Charges and Magnetism opens up the fascinating world of magnetic effects of current. At Myclass24, our solutions for this chapter are crafted with special attention to the vector nature of magnetic force and field — something that trips up a lot of students. Whether it is the Biot-Savart Law, Ampere's Circuital Law, or the working of a galvanometer, our step-by-step solutions help students navigate through every concept with confidence. Also, get subject-wise NCERT Solutions for class 12, for all chapters of Physics, check NCERT Solutions for class 12 Physics.
Find the PDF of NCERT Solutions for Class 12 Physics Chapter 4
Students can download the free PDF of NCERT Solutions for Class 12 Physics Chapter 4 – Moving Charges and Magnetism from Myclass24. The PDF includes fully solved NCERT textbook problems with proper diagrams, vector notations, and formula derivations. It is an ideal companion for CBSE board exam preparation and also serves students preparing for JEE and NEET who need a strong conceptual foundation in magnetism.
Chapter 4 – At a Glance
Detail | Information |
Chapter Name | Moving Charges and Magnetism |
Chapter Number | 4 |
Class | Class 12 |
Subject | Physics |
Total Exercises | 2 (Exercise + Additional) |
Total Questions | 28 |
Important Topics | Biot-Savart Law, Ampere's Law, Lorentz Force, Cyclotron, Galvanometer |
CBSE Marks Weightage | Approx. 8 marks |
PDF Available | Yes – Free Download on Myclass24 |
What is Chapter 4 – Moving Charges and Magnetism About?
Chapter 4 establishes the link between electricity and magnetism through the magnetic force experienced by a moving charge. The Lorentz Force — the combined electric and magnetic force on a charged particle — is introduced early and used throughout the chapter. Students learn to find the direction of force using Fleming's Left-Hand Rule and the cross-product approach.
The Biot-Savart Law gives the magnetic field produced by a small current element. Students apply it to calculate the magnetic field at the centre of a circular loop and along the axis of a current-carrying circular coil. These derivations are expected in five-mark questions.
Ampere's Circuital Law simplifies the calculation of magnetic fields for highly symmetric current distributions — infinite straight conductors, solenoids, and toroids. The derivation of the magnetic field inside a solenoid is a textbook standard.
The chapter also covers the force between two parallel current-carrying conductors (which forms the basis of the SI definition of ampere), the torque on a rectangular current loop in a magnetic field, and the working principle of a moving coil galvanometer. The conversion of a galvanometer into an ammeter or voltmeter is a frequently tested practical topic.
Tricky Aspects of Chapter 4 Students Should Watch
The biggest challenge in this chapter is getting the direction of the magnetic force correct. Students often confuse the direction of the current element, the position vector, and the resulting field direction in Biot-Savart problems. Drawing a clean diagram before solving is essential.
Another frequently misunderstood concept is the motion of a charged particle in combined electric and magnetic fields — particularly the velocity selector and the cyclotron. At Myclass24, our solutions include full derivations of cyclotron frequency and energy, along with annotated diagrams of the cyclotron's D-shaped sections.
FAQs on NCERT Solutions Class 12 Physics Chapter 4-Moving Charges and Magnetism
A moving electric charge generates a magnetic field around it. This relationship forms the foundation of electromagnetism and explains why electric currents create magnetic effects. The chapter introduces magnetic field lines, magnetic force, and the right-hand thumb rule used to determine field direction around a current-carrying conductor. Students learn how moving charges interact with magnetic fields and how this principle is applied in devices such as motors and electromagnets. Understanding the connection between electricity and magnetism is important because it helps explain many practical applications and forms the basis of several numerical and conceptual questions.
The Biot-Savart law helps determine the magnetic field produced by a small current element at a particular point. It shows that the magnetic field depends on the current, distance from the conductor, and orientation of the current element. This law is important because it provides a mathematical method for calculating magnetic fields in different situations. The chapter uses it to derive expressions for magnetic fields due to straight conductors and circular loops. Students frequently encounter numerical problems based on this law, making it an essential concept for board examinations and competitive entrance tests.
When a current-carrying conductor is placed in a magnetic field, it experiences a force due to the interaction between the magnetic field and moving charges. The direction of this force is determined using Fleming’s left-hand rule. The chapter explains how the magnitude of force depends on current, magnetic field strength, and conductor length. This principle is used in electric motors and various electromagnetic devices. Students learn both theoretical concepts and numerical calculations related to magnetic force. Understanding this topic helps explain practical applications of electromagnetism and strengthens problem-solving skills.
A cyclotron is a device used to accelerate charged particles to high speeds using electric and magnetic fields. The magnetic field forces particles to move in circular paths, while an alternating electric field increases their energy. This chapter explains the working principle, construction, and limitations of a cyclotron. Students learn how magnetic force provides the necessary centripetal force for circular motion. Understanding the cyclotron helps connect physics concepts with scientific research and particle acceleration technology. Questions related to its working principle and applications are commonly asked in examinations.