ICSE Class 10 Physics: Electromagnetism — Important Questions with Answers 2026

Short Answer Questions (2-3 Marks)

• Q: What is a magnetic field? How can you determine the direction of magnetic field around a straight conductor?
  Ans: A magnetic field is the region around a magnet or current-carrying conductor where magnetic force can be experienced. Direction is found using the Right-Hand Thumb Rule: If the thumb of the right hand points in the direction of current, the curled fingers give the direction of magnetic field lines around the conductor.
• Q: State Fleming's Left Hand Rule. Where is it used?
  Ans: Fleming's Left Hand Rule: Stretch the thumb, forefinger, and middle finger of the left hand mutually perpendicular. Forefinger → direction of magnetic field (B), middle finger → direction of current (I), thumb → direction of force/motion (F). Used to find the direction of force on a current-carrying conductor in a magnetic field — principle of electric motor.
• Q: Explain the principle and working of a DC motor.
  Ans: Principle: A current-carrying conductor placed in a magnetic field experiences a force (F = BIl). Working: Current flows through a rectangular coil ABCD placed between poles of a magnet. By Fleming's Left Hand Rule, forces on AB and CD are in opposite directions, creating a torque that rotates the coil. The commutator (split ring) reverses current direction every half turn, maintaining continuous rotation.
• Q: What is electromagnetic induction? State Faraday's laws.
  Ans: Electromagnetic induction is the phenomenon of generating EMF (and hence current) in a conductor by changing the magnetic flux linked with it. Faraday's Laws: (1) Whenever magnetic flux linked with a coil changes, an EMF is induced. (2) The magnitude of induced EMF is directly proportional to the rate of change of magnetic flux. e = -dφ/dt.
• Q: State Lenz's Law. How does it follow from conservation of energy?
  Ans: Lenz's Law states: The direction of induced current is such that it opposes the change in magnetic flux that causes it. It follows conservation of energy because: if the induced current aided the change, it would increase the flux further, inducing more current — creating energy from nothing, violating conservation of energy.

Long Answer / Application Questions (4-6 Marks)

• Q: Explain the principle of a simple AC generator.
  Ans: Principle: Electromagnetic induction — when a coil rotates in a magnetic field, the magnetic flux through the coil changes continuously, inducing an alternating EMF. Key parts: Armature coil, strong magnets, slip rings, brushes. The EMF varies sinusoidally: e = e₀ sin(ωt). Slip rings (not split rings) maintain continuous contact, producing AC output.
• Q: State Fleming's Right Hand Rule. Where is it used?
  Ans: Fleming's Right Hand Rule: Stretch the thumb, forefinger, and middle finger of the right hand mutually perpendicular. Thumb → direction of motion, forefinger → direction of magnetic field, middle finger → direction of induced current. Used to find the direction of induced current in a generator.
• Q: Differentiate between AC and DC.
  Ans: AC (Alternating Current): magnitude and direction change periodically, generated by AC generator using slip rings, can be transmitted over long distances with less loss (via transformers), used in homes and industries. DC (Direct Current): flows in one direction only, generated by cells/batteries or DC generator using commutator, cannot be easily transmitted, used in electronic devices.

Exam Tips for This Chapter

• Revise all definitions and laws from Electromagnetism — they are commonly asked as 1-2 mark questions
• Practice diagrams related to Electromagnetism — neat labelled diagrams carry 2-3 marks
• For numericals, always show formula → substitution → answer with correct units
• Previous year analysis shows Electromagnetism carries 8-12 marks in the board exam