Electric Motor, Electromagnetic Induction and Electric Generator — Class 10 Science (CBSE) explained

What you’ll learn

1. 1

   Lesson 1: Electric Motor: From Current to Rotation

   6 min
   • An Electric Motor Converts Electrical Energy into Mechanical EnergySchool assessment
   • Locate the Coil, Split Ring and BrushesSchool assessment
   • Opposite Forces Turn the CoilSchool assessment
   • The Split Ring Keeps Rotation in the Same DirectionSchool assessment
   • Commercial Motors Use an ArmatureSchool assessment
   • Explain the Motor as a Connected SequenceSchool assessment
   • Can Motion in a Magnetic Field Produce Current?School assessment
   • A Moving Magnet Produces Momentary CurrentSchool assessment
2. 2

   Lesson 2: Electromagnetic Induction: Change Produces Current

   6 min
   • Moving the Coil Also Produces CurrentSchool assessment
   • Read Current Direction with a GalvanometerSchool assessment
   • Faraday Builds an Interest in ScienceNot assessed
   • Use a Current-Carrying Coil Instead of a Moving MagnetSchool assessment
   • Starting and Stopping Current Produce Opposite DeflectionsSchool assessment
   • A Changing Magnetic Field Causes InductionSchool assessment
   • Two Ways to Induce Current in a CoilSchool assessment
   • Use Fleming's Right-Hand RuleSchool assessment
3. 3

   Lesson 3: Electric Generator and Board-Essential AC and DC

   6 min
   • A Generator Uses Mechanical Energy to Produce ElectricitySchool assessment
   • Two Rings Connect the Rotating Coil to Stationary BrushesSchool assessment
   • Clockwise Rotation Produces the First Current DirectionSchool assessment
   • Current Reverses After Every Half RotationSchool assessment
   • A Split-Ring Commutator Produces Unidirectional CurrentSchool assessment
   • Board Essential: Distinguish DC from AC by Direction
   • Board Essential: Fifty Hertz and Long-Distance Transmission
   • Recap: Separate Board Essentials from Formative Understanding

Key concepts

The split ring keeps rotation in the same direction

A device that reverses the direction of current through a circuit is called a commutator.

Commercial motors

The soft iron core alone is not the complete armature.

Moving-coil observations

The important comparison is motion of the magnet relative to the coil.

Cause of electromagnetic induction

The cause is the change in the magnetic field associated with the secondary coil.

Direct-current generation

The device is called a direct current generator.

Board-essential DC and AC

A current that reverses its direction periodically is alternating current.

Exam focus

Board exam

CBSE assesses this chapter in the 2026-27 year-end board examination.

Syllabus

From the Magnetic effects of current syllabus: Direct current. Alternating current: frequency of AC. Advantage of AC over DC. Formative only: Motor, Electromagnetic Induction, Electric Generator.

Formative only

Assessed in school but not in the board exam: An Electric Motor Converts Electrical Energy into Mechanical Energy, Locate the Coil, Split Ring and Brushes, Opposite Forces Turn the Coil, The Split Ring Keeps Rotation in the Same Direction, Commercial Motors Use an Armature, Explain the Motor as a Connected Sequence, Can Motion in a Magnetic Field Produce Current?, A Moving Magnet Produces Momentary Current, Moving the Coil Also Produces Current, Read Current Direction with a Galvanometer, Use a Current-Carrying Coil Instead of a Moving Magnet, Starting and Stopping Current Produce Opposite Deflections, A Changing Magnetic Field Causes Induction, Two Ways to Induce Current in a Coil, Use Fleming's Right-Hand Rule, A Generator Uses Mechanical Energy to Produce Electricity, Two Rings Connect the Rotating Coil to Stationary Brushes, Clockwise Rotation Produces the First Current Direction, Current Reverses After Every Half Rotation and A Split-Ring Commutator Produces Unidirectional Current.

Not assessed

These parts go beyond the 2026-27 syllabus and are taught for understanding only: Faraday Builds an Interest in Science.

Exam note

Board-assessed: direct current, alternating current, frequency of AC (50 Hz in India), advantage of AC over DC (section 3.3, last paragraph). These complete the board syllabus of textbook Chapter 12, whose current edition does not cover them.

Paper pattern

80 marks, 3 hours, 39 questions in three sections (A Biology, B Chemistry, C Physics); internal assessment 20. Units: I Chemical Substances 25, II World of Living 25, III Natural Phenomena 12, IV Effects of Current 13, V Natural Resources 5.

Question style

About 50% of board questions are competency-focused: case-based, source-based, integrated, data interpretation, situational and application-oriented.

Practice in the app

69 board-pattern questions with marking schemes: 21 multiple choice (1 mark), 11 assertion–reason (1 mark), 14 very short answer (2 marks), 12 short answer (3 marks), 3 long answer (5 marks) and 8 case-based (4 marks).

Sample questions with marking points

Board-pattern questions from the AI Lessons practice set for this chapter. The marking points show what an examiner looks for; full model answers are in the app.

1. Very short answer2 marks

   The north pole of a magnet approaching end B of a stationary coil gives a right deflection. Predict the deflection when the north pole is withdrawn and when it is held at rest near B. State what each reading indicates about current.

   Marking points

   • Withdrawal produces a left deflection.0.5
   • The induced current is opposite to that during approach.0.5
   • Holding the magnet at rest produces zero deflection.0.5
   • Zero deflection indicates no current in the coil circuit.0.5

2. Short answer3 marks

   A teacher closes the primary-coil key and observes a momentary secondary deflection. Explain why the pointer returns to zero after closing, deflects oppositely during opening, and returns to zero again after opening.

   Marking points

   • After closing, steady primary current produces an unchanging magnetic field, so no secondary current is induced.1
   • During opening, the magnetic field changes in the opposite sense to starting, producing an opposite induced current and deflection.1
   • After the primary current reaches zero, the magnetic field no longer changes, so the secondary deflection becomes zero.1

Frequently asked questions

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