Pre-Maxwell Electrodynamics

This book provides a clear and simplified understanding of the fundamental ideas of electricity and magnetism that existed before Maxwell unified them into modern electromagnetism. Written in easy language and supported by concept-based explanations, question-answer format, and MCQs, it helps readers build strong foundational knowledge in electrodynamics.

We begin with electrostatics, where charges are at rest. Using Coulomb's law, we learn how charges interact and how the force depends on magnitude, distance, and the nature of charges. This leads naturally to the concept of the electric field, defined as the force per unit test charge. The book explains why this idea was introduced, the difference between source charge and test charge, and why the test charge must be very small.

Next, the book introduces Gauss's law, which relates electric flux through a closed surface to the enclosed charge. The properties of the electrostatic field are then explained, including why it is conservative (zero curl), how electric potential is defined, and why the relation E=−∇VE = -\nabla VE=−∇V shows that electric field always points "downhill" in potential.

We then move to magnetostatics, the study of magnetic fields from steady currents. The Biot-Savart law describes how a current element produces a magnetic field, while Ampère's law gives a powerful method to calculate magnetic fields in symmetric situations. Key properties such as closed magnetic field lines, the absence of magnetic monopoles, and the relation ∇×B=μ0J\nabla\times B = \mu_0 J∇×B=μ0J are described clearly.

The book then explains Faraday's law of electromagnetic induction, one of the most important discoveries in physics. A changing magnetic field produces a circulating electric field, leading to induced emf and current. This makes the electric field non-conservative in electrodynamics, since ∇×E≠0\nabla\times E \neq 0∇×E=0. Everyday applications such as generators and transformers connect theory with real life.

A major highlight of the book is the explanation of the failure of the original Ampère's law when applied to time-varying situations. Using the example of a charging capacitor, it is shown that Ampère's law predicts contradictory magnetic fields depending on the chosen surface. This inconsistency revealed the need for modification.

Maxwell's revolutionary idea of displacement current-a current produced not by moving charges but by a changing electric field-solves this problem. Adding the displacement current term leads to the Ampère-Maxwell law, which works for both steady and time-varying fields and satisfies charge conservation. This correction ultimately paved the way for the existence of electromagnetic waves.

The book concludes with a comprehensive collection of conceptual questions, long answers, and 27 MCQs, all designed for quick revision and deep understanding.

This book is ideal for students of physics at the undergraduate level, competitive exam aspirants, and anyone seeking a simplified yet complete foundation in electrodynamics before Maxwell's equations.