Class XII notes / Electromagnetic Induction
Everything you need for Class 12 CBSE and NEET electromagnetic induction (EMI), in the order you should study it: laws, motional emf, formulas, practice, practicals and the chapters that come next.
Last updated: November 2026
Each step builds on the last. Read the page, then do a few questions before moving on.
Start with the full Class XII chapter notes for the big picture: flux, induced emf, eddy currents, inductance.
Chapter 6: Electromagnetic Induction notes · EMI & Alternating Current sectionUnderstand magnetic flux and why a changing flux creates an emf.
Faraday’s laws of electromagnetic inductionFind the direction of the induced current and see how it follows conservation of energy.
Lenz’s law and induced current in magnetic fieldsRod on rails, ε = BLv, induced current, power used, and the hand rules.
Motional emf, induced current & power used · What is motional emf? How to find its direction?Apply the formulas to MCQs, numericals and previous-year questions.
Go to the practice sectionThe generator is EMI at work, and it leads straight into AC circuits.
Alternating Current notesQuick reference for revision. Units are SI.
| Quantity | Formula | Remember |
|---|---|---|
| Magnetic flux | Φ = BA cos θ | Unit: weber (Wb); θ is the angle between B and the area normal |
| Faraday’s law | ε = −N dΦ/dt | The minus sign is Lenz’s law |
| Induced current | I = ε/R | R is the total circuit resistance |
| Charge flown | q = ΔΦ/R | Independent of how fast the flux changes |
| Motional emf | ε = BLv | B, L and v mutually perpendicular; otherwise ε = BLv sin θ |
| Force on the rod | F = B²L²v/R | Always opposes the motion |
| Power used | P = B²L²v²/R = I²R | Mechanical power equals heat produced |
| Rotating rod | ε = ½BωL² | ω = 2πf |
| Terminal velocity | v = mgR/(B²L²) | Rod sliding down vertical rails |
| Self-inductance | ε = −L dI/dt | Energy stored: U = ½LI² |
| Mutual inductance | ε₂ = −M dI₁/dt | Unit of L and M: henry (H) |
| Solenoid inductance | L = μ₀n²Al | n = turns per unit length |
Want the full derivations behind these? Open the motional emf article and the chapter notes. Need a quick answer? Try the Class 12 physics calculators.
Solve in this order: concept questions, numericals, then previous-year questions under a timer.
Editor’s note: the PYQ list does not yet have an Electromagnetic Induction page. Publish it, then link it here as the first item.
It is the production of an emf (and a current in a closed circuit) whenever the magnetic flux through a circuit changes. The flux can change because the field changes, the area changes, or the orientation changes.
Faraday’s law gives the size of the induced emf: ε = −dΦ/dt. Lenz’s law gives the direction: the induced current opposes the change that causes it. Together they appear as the minus sign in Faraday’s law.
It is the emf induced across a conductor because it moves in a magnetic field. For a rod of length L moving at speed v perpendicular to a field B, ε = BLv. Read the full explanation and direction rules.
Moving Charges and Magnetism before it, and Alternating Current after it. Questions often mix them, for example a generator, a transformer or an LCR circuit with an induced emf.
In the formula sheet above and in the chapter notes.
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