Overview

Electromagnetic Induction is one of the most consistently high-weightage chapters in Grade XII Physics, and it’s also one of the broadest — it pulls together Faraday’s and Lenz’s laws, induced emf in moving conductors and rotating coils, self and mutual inductance, energy stored in an inductor, and transformers, all under one roof. Nearly every board paper draws at least one theory question asking you to state Lenz’s law and explain how it satisfies conservation of energy, alongside a derivation of emf induced in a rectangular coil rotating in a magnetic field — a proof worth memorizing step by step since it appears almost every year in some form.

The numericals split into a few recognizable families: instantaneous emf from a time-varying flux equation (differentiate φ with respect to t), emf induced in a straight conductor moving through a field (using v, B, and length or angle), self-inductance of a solenoid, and transformer turn-ratio problems involving efficiency and power. The eddy currents and transformer short-answer questions also recur reliably — particularly why laminated cores reduce heating, and why transformers don’t work on DC.

Below is the full set of MCQs, theory questions, and numerical problems from past NEB board exams, organized by course and question type.

⚠️ Common Mistakes Students Make

• Confusing Faraday’s law (magnitude) with Lenz’s law (direction). Faraday’s law tells you how much emf is induced (rate of change of flux); Lenz’s law tells you which direction it opposes. Answering “state Faraday’s law” with only the magnitude relation, omitting the negative sign that encodes Lenz’s law, is a common partial-mark loss.
• Mixing up self-inductance and mutual inductance formulas. Self-inductance relates a coil’s own changing current to its own induced emf; mutual inductance relates one coil’s changing current to emf induced in a separate, nearby coil. Students often apply the self-inductance formula (L = N²μ₀A/l) when a mutual inductance problem is being asked.
• Forgetting that transformers only work on AC. Since a transformer relies on a changing flux to induce emf in the secondary coil, a steady DC current produces no changing flux — a frequently tested short-answer trap.