# Electromagnetic Induction Notes, Class 12 Physics | SwaVid Electromagnetic Induction, NCERT Class 12 Physics: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/physics/chapter/electromagnetic-induction Source: https://www.swavid.com/cbse/class-12/physics/chapter/electromagnetic-induction # Electromagnetic Induction ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Physics on SwaVid ### Magnetic flux ### Faraday's law of induction ### Lenz's law and energy conservation ### Motional electromotive force ### Inductance ### AC generator ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Physics › Electromagnetic Induction Notes written by SwaVid from the NCERT textbook. Class 12 Physics, Chapter 6. Key ideas, formulas and common mistakes. CBSE prints 17 marks for Units III-IV together, not for this chapter alone. Short answer. This chapter covers the generation of electric currents using changing magnetic fields through the phenomenon of electromagnetic induction. Students learn how Faraday's experiments, Lenz's law, motional emf, and inductance explain the working of electrical devices like AC generators. Source: NCERT Physics Part I (Reprint 2026-27) , Chapter 6, Electromagnetic Induction Magnetic flux measures the total number of magnetic field lines passing through a given surface area. It depends on the magnetic field strength, the surface area, and the angle between the field and the area normal. An electromotive force is induced in a circuit whenever the magnetic flux linked with the circuit changes with time. The magnitude of the induced emf is directly proportional to the time rate of change of magnetic flux. The polarity of the induced emf is always such that it tends to produce a current which opposes the change in magnetic flux that produces it. This opposition is a direct consequence of the principle of conservation of energy. An emf is induced across the ends of a straight conductor when it moves across a magnetic field. This happens because the magnetic force acts on the free conducting electrons inside the moving rod. Inductance is the property of an electric circuit by which an emf is induced due to a change in current. Mutual inductance involves two interacting coils, while self-inductance involves a single coil opposing changes in its own current. An AC generator converts mechanical energy into electrical energy by rotating a coil in a uniform magnetic field. As the effective area facing the field changes sinusoidally, it produces an alternating electromotive force. Try each question first. Then tap it to see the answer. Area of the loop A = (0.1 m)² = 0.01 m² Since the loop is perpendicular to the field, the normal is parallel to the field, so θ = 0° ΦB = B A cos 0° = 0.2 × 0.01 × 1 = 0.002 Wb 0.002 Wb Change in flux ΔΦB = 0.02 - 0.08 = -0.06 Wb Time interval Δt = 0.1 s |ε| = |ΔΦB / Δt| = |-0.06 / 0.1| = 0.6 V 0.6 V Identify given values: l = 0.5 m, v = 4 m s⁻¹, B = 0.3 T Apply motional emf formula ε = B l v ε = 0.3 × 0.5 × 4 = 0.6 V 0.6 V Alternating Current . Moving Charges and Magnetism . Magnetism and Matter . The 14 chapters of Class 12 Physics . CBSE does not give marks to one chapter. It prints 17 marks for Units III-IV together (Magnetic Effects of Current and Magnetism; Electromagnetic Induction and Alternating Currents). Electromagnetic Induction is part of that group. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Alternating Current. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 6 NCERT book - 17 marks, Units III-IV together - 3 quick checks - Using the plane of the coil instead of its normal to calculate magnetic flux . Always measure the angle θ between the magnetic field vector and the normal to the area plane. If the field is parallel to the surface, the angle with the normal is 90 degrees, making flux zero. - Assuming an induced emf requires a closed electrical circuit . An induced emf develops whenever magnetic flux changes across an area, even in an open circuit or isolated moving rod. Induced current requires a closed conducting path, but emf does not. - Neglecting the negative sign in Faraday-Lenz law calculations . Keep the negative sign to correctly show that the induced emf opposes the change in flux. When only the magnitude of induced emf is required, write |ε| = |dΦB / dt|. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup) - [All 14 chapters](https://www.swavid.com/cbse/class-12/physics/chapters) - [NCERT Physics Part I (Reprint 2026-27)](https://ncert.nic.in/textbook.php?leph1=0-8) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/alternating-current) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/moving-charges-and-magnetism) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/magnetism-and-matter) - [Class 12 Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup)