Electric Motor, Electromagnetic Induction and Generator Class 10
Updated 14 October 2026 · Fact-checked
Assessed in school only, not in the board exam.
An electric motor turns electrical energy into mechanical energy, with a split ring reversing the coil current every half turn. Electromagnetic induction is the reverse idea: a changing magnetic field induces a current, which a generator uses to make AC or DC. This is assessed in school, not in the board exam.
Notice the copper disk D turning between the magnet's poles: this motion makes a current flow, which is electromagnetic induction in a generator.
Picture: Émile Alglave · Public domain · Wikimedia Commons
Understand Electric Motor, Electromagnetic Induction and Generator
This topic is assessed in school only, not in the board exam. It comes from the CBSE Reading Material for 2026-27 and extends the Magnetic Effects of Electric Current chapter.
Electric motor. A motor converts electrical energy into mechanical energy; fans, mixers, washing machines and refrigerators all use one. A rectangular coil ABCD sits between the poles of a magnet, with arms AB and CD at right angles to the field. Current enters through brush X, so it flows A to B in one arm and C to D, the opposite way, in the other. By Fleming's left-hand rule the two arms are pushed in opposite directions (AB down, CD up), so the coil turns. After half a turn the two halves of the split ring swap brushes, the current in the coil reverses, and so do the forces, which keeps the coil turning the same way. A device that reverses current like this is a commutator. Real motors are stronger because they use an electromagnet, many turns of wire and a soft iron core; the core with its coil is the armature.
Electromagnetic induction. Faraday found in 1831 that moving a magnet towards a coil joined to a galvanometer makes the needle jump; moving it away deflects it the other way; when nothing moves, there is no current. The same happens if a current in a nearby coil is switched on or off. So a changing magnetic field linked with a conductor induces a current in it. The induced current is largest when the conductor moves at right angles to the field, and Fleming's right-hand rule gives its direction: forefinger along the field, thumb along the motion, middle finger along the induced current.
Generator. A generator uses mechanical energy to rotate a coil in a magnetic field. The coil's ends are joined to two full rings (often called slip rings), each pressed by its own brush, so the current in the external circuit reverses every half turn: an AC generator. With a split-ring commutator, one brush always touches the arm moving up, so the current flows one way: a DC generator. In India, AC has a frequency of 50 Hz, changing direction every 1/100 second, and it can be sent over long distances without much loss.
Electric Motor, Electromagnetic Induction and Generator: formulas and key facts
- Motor energy change
- A generator does the reverse: mechanical energy to electrical energy.
- Fleming's left-hand rule (motor)
- Use it to find which way each arm of the motor coil is pushed.
- Fleming's right-hand rule (generator)
- Valid when the conductor moves at right angles to the field.
- Commutator
- Keeps a motor turning one way; makes a generator give DC.
- AC in India
- Two reversals in each cycle: 50 cycles a second means 100 reversals a second.
- Ways to induce a current
- Moving a magnet near a coil, or switching the current in a nearby coil on or off.
Electric Motor, Electromagnetic Induction and Generator in real life
Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.
Electromagnetic induction
Suppose a bicycle has a small dynamo that runs a front lamp: a magnet inside it spins next to a fixed coil whenever the wheel turns it. While you ride, the lamp glows; when you stop, it goes out.
Using electromagnetic induction, explain why the lamp glows only while the cycle moves. Which rule would give the direction of the induced current in a wire moving at right angles to a magnetic field?
Try it first, then show the solutionSolution
- A current is induced in a coil only when the magnetic field linked with it changes.
- While the wheel turns the magnet, the field around the fixed coil keeps changing, so a current is induced and the lamp glows.
- When the cycle stops, the magnet stops, the field no longer changes, and the induced current drops to zero, as the galvanometer reading did in Faraday's activity.
- For a straight conductor moving at right angles to a field, Fleming's right-hand rule gives the direction: forefinger along the field, thumb along the motion, middle finger along the induced current.
Answer: A current is induced in a coil only when the magnetic field linked with it changes. While the wheel spins the magnet, the field around the fixed coil keeps changing, so a current flows and the lamp glows. When the cycle stops, the field stops changing and the induced current falls to zero, just as the galvanometer read zero in Faraday's activity when nothing moved. For a wire moving at right angles to a field, Fleming's right-hand rule gives the direction of the induced current.
Memory hook: No change, no current: the dynamo lamp needs a moving magnet.
Tricks to remember Electric Motor, Electromagnetic Induction and Generator
Short memory aids. Say each one aloud once, then use it on a question the same day.
Left for Motors, Right for generators
Left hand: motor (force on a current). Right hand: generator (induced current).
Use it when: Choosing the correct Fleming's rule.
Split for straight, slip for swing
Split ring: current keeps one direction (motor, DC generator). Slip rings: current swings both ways (AC generator).
Use it when: AC versus DC generator questions.
50 cycles, 100 flips
AC in India: 50 Hz, so the direction flips every 1/100 second.
Use it when: Recalling the frequency fact.
Exam tips
- Learn to describe the motor and the generator in order: parts, how current flows, what happens after half a turn, and why.
- Keep the two Fleming's rules apart: name the hand and state what each finger stands for.
- In activity-based questions, describe the galvanometer: which way it deflects, and that it reads zero when nothing moves.
Test your recall
Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.
1.What energy change takes place in an electric motor?Show answer
Electrical energy is converted into mechanical energy.
2.What is the role of the split ring in a motor?Show answer
It acts as a commutator, reversing the current in the coil every half rotation so the coil keeps turning the same way.
3.What is an armature?Show answer
The soft iron core together with the coil wound on it.
4.Who discovered electromagnetic induction, and when?Show answer
Michael Faraday, in 1831.
5.When is the induced current largest?Show answer
When the conductor moves at right angles to the magnetic field.
6.What is the frequency of AC in India?Show answer
50 Hz; it changes direction every 1/100 second.
Electric Motor, Electromagnetic Induction and Generator: frequently asked questions
Is the electric motor or generator in the Class 10 board exam?
No. For 2026-27, the electric motor, electromagnetic induction and the generator are taught from the CBSE Reading Material and assessed in school only, through internal or formative assessment. They are not set in the board theory paper.
What is the difference between an AC and a DC generator?
An AC generator uses two slip rings, so the current in the external circuit reverses every half rotation. A DC generator uses a split-ring commutator, so one brush always touches the arm moving up and the current flows in one direction.
Why is AC preferred for supplying power?
Electric power can be transmitted over long distances as AC without much loss of energy, which is why most power stations today produce AC.