Lecture 34: Magnetism, Magnetic Field & Magnetic Force | Physics for Engineers | Dr. Imran Malik

Introduction to Magnetism, Magnetic Field & Magnetic Force | Physics Lecture 34 This lecture marks the beginning of a new section in Electromagnetism—Magnetism. Students are introduced to the fascinating history of magnetism, the origin of magnetic phenomena, and the fundamental concepts that govern magnetic fields and magnetic forces. The lecture provides a conceptual bridge between Electrostatics, Electrodynamics, and Magnetism, preparing students for advanced topics such as Gauss's Law of Magnetic Field (Second Maxwell's equation) Ampère's Law (Third Maxwell's equation), Faraday's Law of Induction (Fourth Maxwell's equation). The lecture begins with a detailed discussion of the history of magnetism, from naturally occurring lodestones to the modern understanding of magnetic fields. An overview of the entire magnetism section is presented so students can appreciate how the different topics are connected. Before introducing magnetic fields, the lecture briefly presents the second, third, and fourth Maxwell's Equations in their mathematical forms and explains their physical significance. Particular emphasis is placed on Gauss's Law for Magnetism, which states that the net magnetic flux through any closed surface is zero, implying that magnetic monopoles have never been observed. Students learn why a magnetic field cannot be defined using a permanent magnet alone, unlike the electric field, and why the definition of magnetic field is instead based on the force experienced by a moving electric charge. The lecture then develops the expression for the magnetic force acting on a moving charge, introducing the microscopic variables charge (q), velocity (v), and magnetic field (B). The vector nature of the magnetic force, the right-hand rule, and the dependence of magnetic force on the angle between velocity and magnetic field are discussed in detail. Several conceptual examples and numerical problems help students apply the magnetic force equation to real physical situations. An important concept discussed in this lecture is that the magnetic force does no work because it is always perpendicular to the velocity of the moving charge. Students compare electric forces and magnetic forces, highlighting the fundamental differences between electric and magnetic fields and understanding why electric fields can change a particle's speed while magnetic fields only change its direction of motion. Finally, the lecture studies the motion of a charged particle in a uniform magnetic field. By equating the magnetic force to the centripetal force, students derive expressions for the radius of circular motion, time period, angular velocity, and frequency (cyclotron frequency). It is also shown mathematically that particles having the same charge-to-mass ratio (q/m) possess the same time period and angular frequency in a given magnetic field, regardless of their speed. This principle forms the basis of several important scientific instruments, including the cyclotron and mass spectrometer. Throughout the lecture, mathematical derivations, conceptual discussions, graphical explanations, and examination-oriented numerical problems help students develop a solid foundation in magnetism. Topics Covered Introduction to Magnetism History of Magnetism Overview of the Magnetism Section Maxwell's Equations (Brief Introduction) Gauss's Law for Magnetism Magnetic Monopoles Magnetic Flux Magnetic Field Magnetic Field Due to a Moving Charge Lorentz Magnetic Force Magnetic Force on a Moving Charge Right-Hand Rule Vector Nature of Magnetic Force Numerical Problems on Magnetic Force Magnetic Force Does No Work Electric Force vs Magnetic Force Motion of a Charged Particle in a Uniform Magnetic Field Radius of Circular Motion Time Period of Circular Motion Angular Velocity Cyclotron Frequency Charge-to-Mass Ratio (q/m) Examination-Oriented Numerical Problems Recommended Textbooks Physics for Scientists and Engineers — Raymond A. Serway and John W. Jewett, Jr. University Physics with Modern Physics — Hugh D. Young and Roger A. Freedman Fundamentals of Physics — David Halliday, Robert Resnick, and Jearl Walker This lecture is part of PHY-101 and PHY-102 (Basic Physics) courses for undergraduate students. Keywords Magnetism, Magnetic Field, Magnetic Force, Lorentz Force, Moving Charge in Magnetic Field, Gauss's Law for Magnetism, Maxwell's Equations, Magnetic Monopoles, Magnetic Flux, Right-Hand Rule, Charged Particle Motion, Circular Motion in Magnetic Field, Cyclotron Frequency, Charge-to-Mass Ratio, Radius of Circular Motion, Electromagnetism, Engineering Physics, University Physics, Physics Lecture, Basic Physics, PHY-101, PHY-102, Physics Tutorial #Physics #Magnetism #MagneticField #MagneticForce #LorentzForce #MaxwellsEquations #GaussLawForMagnetism #Electromagnetism #EngineeringPhysics #UniversityPhysics #PhysicsLecture #BasicPhysics #PHY101 #PHY102 #STEM