Irodov Part 3 Electrodynamics — Which Problems to Solve for JEE

A section-by-section map of Part Three of I.E. Irodov’s Problems in General Physics, checked against the JEE Main and JEE Advanced syllabuses.

Part Three is the largest part of the book at 407 problems, and it carries roughly 315 problems worth attempting — as much in-scope work as the whole of Mechanics. Students rarely get here, because it sits behind Part One’s relativity section and Part Two’s statistical mechanics, and that is a real loss: electrostatics, current and induction are where Advanced concentrates its hardest markable physics.

No section here is off the syllabus outright. Four are wholly in scope and three need picking through, but even the three have a high usable fraction. If your time for Irodov is limited and you have finished Part One, come straight here rather than working forwards through Part Two.

Key insight. The dividing line running through this part is between fields in matter and fields and currents you can compute. Irodov spends a great deal of effort on polarisation, bound charge and magnetisation — a whole theory the JEE syllabus replaces with “a parallel plate capacitor, with or without a dielectric”. Recognise that theory and turn the page.

The sections at a glance

Section 3.1 — Constant Electric Field in Vacuum

Fifty-three problems, all usable. Coulomb’s law, field and potential, dipoles, flux and Gauss’s law. The Advanced syllabus limits Gauss applications to the infinite wire, the plane sheet and the spherical shell; Irodov goes further, but the method is identical and the extra geometries are good practice rather than wasted effort.

Its real contribution is superposition by integration — charged rods, rings, arcs and discs — which is the technique Advanced reaches for when it wants to separate candidates on electrostatics.

Before you start it: Electric Charges and Fields.

Section 3.2 — Conductors and Dielectrics in an Electric Field

Forty-seven problems, of which roughly twenty-one are usable. The conductor half is in scope: induced charges, earthed spheres, the method of images, field just outside a conductor. The dielectric half is not — bound and polarisation charge, the displacement vector $\vec{D}$ and boundary conditions at a dielectric interface form a theory the syllabus does not carry.

Solve the conductor, induced-charge and image problems. Skip anything naming polarisation, bound charge, susceptibility or $\vec{D}$.

Section 3.3 — Electric Capacitance. Energy of an Electric Field

Forty-six problems, all in scope: capacitance, series and parallel combinations, dielectric slabs in parallel plate capacitors, and energy stored. Irodov’s energy-method problems — where a plate is moved or a slab withdrawn and you are asked for the work done — are the ones worth the time.

Before you start it: Electrostatic Potential and Capacitance.

Section 3.4 — Electric Current

Seventy-two problems, all in scope, and the third-largest fully usable section in the book after 4.1 Mechanical Oscillations and 1.3 Conservation Laws. Ohm’s law, resistor networks, Kirchhoff’s laws, heating effects and transient RC circuits. Note that the potentiometer is not on the JEE Main syllabus, though it remains fair game for Advanced.

Before you start it: Current Electricity.

Section 3.5 — Constant Magnetic Field. Magnetics

Sixty-nine problems, of which roughly forty-eight are worth doing — second only to 3.6 among the sections that need picking through. The section has two halves and the title tells you so.

Solve everything in the first half: Biot–Savart, Ampère’s law, fields of wires, loops and solenoids, forces on currents, and the magnetic moment of a loop. Skip the “Magnetics” half — magnetisation, the $\vec{H}$ field, susceptibility, ferromagnetism and hysteresis are on neither syllabus, and the magnetic properties of materials are on neither syllabus.

Before you start it: Moving Charges and Magnetism.

Section 3.6 — Electromagnetic Induction. Maxwell’s Equations

Eighty-four problems — the second-largest section in the book, behind only 4.1 — of which about fifty-nine are usable, the largest usable pool of any section that needs picking through. Faraday’s law, Lenz’s law, motional EMF, self and mutual inductance, and LR, LC and LCR circuits with direct and alternating sources are all named on the syllabus.

Solve all of that. Skip the Maxwell’s equations material at the end of the section: displacement current in its full form, field transformations between frames, and anything asking you to verify one of the four equations.

Before you start it: Electromagnetic Induction and Alternating Current.

Section 3.7 — Motion of Charged Particles in Electric and Magnetic Fields

Thirty-six problems, of which perhaps sixteen are usable. The syllabus carries the force on a moving charge, which covers the circular and helical motion problems and the crossed-field ones.

Skip the accelerator physics that fills the rest: the cyclotron — on neither syllabus — the betatron, magnetic focusing and mass spectrometry.

Common mistakes with Part Three

Never arriving. This is the largest mistake and it is one of sequencing. A student working the book in order meets 49 relativity problems and 51 statistical mechanics problems before reaching the single richest part for JEE. Come here after Part One.

Working 3.2 straight through. The dielectric theory in the back half is genuinely demanding and entirely unexaminable, which makes it the most expensive false trail in the book.

Reading 3.5 and 3.6 as two hard sections rather than four halves. Each splits cleanly into an in-scope half and an out-of-scope half. Between them they hold about 107 usable problems — comparable to the whole of Optics — but only if you stop at the right point.

Doing 3.4 quickly because circuits feel easy. Seventy-two problems with no skips is the densest usable block in Irodov, and its transient-circuit problems are harder than they look.

What to read next

• Part 4 — Oscillations and Waves, which holds the book’s largest fully in-scope section
• Part 1 — Mechanics
• Should you solve Irodov at all?