Class 12 Physics Electromagnetic Induction Notes and Important Questions
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Notes for Class 12 Electromagnetic Induction (Physics) are shown above.
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Important Questions
State Lenz law in electromagnetism. Justify this law in favor of the principle of conservation of energy.
A magnet is quickly moved in the direction indicated by an arrow between two coils $C_1$ and $C_2$ as shown in the figure. What will be the direction of induced current in each coil as indicated by the movement of magnet? Explain.
Lenz law gives the direction of induced emf.
i) State Lenz law.
ii) Explain how this law is in accordance with the law of conservation of energy.
Obtain a relation for the energy stored in an inductor.
A step down transformer converts a voltage of 2200 Volt into 220 Volt in the transmission line. Number of turns in the primary coil is 5000. Efficiency of the transformer is 90% and its output power is 8 KW. Calculate:
i) Number of turns in the secondary coil.
ii) Input power.
State Lenz's law.
Plot a graph to show the variation of induced emf in a coil rotating in a uniform magnetic field with time.
Derive an expression for the energy stored in an inductor.
Self inductance of a coil varies as
Reciprocal of number of turns
Resistance of the coil
Square of number of turns
Magnitude of current flowing
State Law of electromagnetic induction
Explain the significance of the negative sign
State what the symbols ε and dϕ/dt represent in the equation.
Two identical copper balls are dropped from the same height as shown in the figure. Ball P passes through a region of uniform horizontal magnetic filed of flux density B. Explain why ball P takes longer than ball Q to reach the ground.
Define self inductance of a coil.
A current from A to B is increasing in magnitude. What is the direction of induced current, if any, in the loop as shown in figure? Justify.
Calculate the self inductance of a coil of 100 turns if a current of 2A gives rise to magnetic flux of 5×10⁻³ Weber through the coil.
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Exam
Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
4
Question Items
2
Total Marks
3
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2082 | 1 | 1 |
| 2081 | 2 | — |
| 2080 | 1 | 1 |
Also appears in 3 model questions (not counted above — model sets aren't actual NEB exam history).
The phenomenon of producing electricity through changing magnetic fields is explored here. Key topics include Faraday's law, Lenz's law, motional emf, generators, eddy currents, self and mutual inductance, and transformers.
This page covers Electromagnetic Induction, chapter 18 of 25 in the Class 12 Physics syllabus set by the National Examination Board (NEB). 10 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.