ICSE Class 10 Physics: Electromagnetism — Complete Notes 2026

Magnetic Effect of Electric Current

• Oersted's experiment: current-carrying wire deflects compass needle
• Right-hand thumb rule: curl fingers in direction of current; thumb points north
• Magnetic field lines around a straight wire and a solenoid

Force on a Current-Carrying Conductor

• Fleming's left-hand rule: thumb=force, index=field, middle=current
• F = BIL sin θ; torque on a current loop in magnetic field
• DC motor principle: force on coil causes rotation

DC Motor — Construction and Working

• Parts: armature coil, permanent magnet, split-ring commutator, brushes
• Working: current through coil → force (BIL) → rotation → commutator reverses current to maintain rotation direction
• Energy conversion: electrical energy → mechanical energy

Electromagnetic Induction

• Faraday's law: EMF induced = rate of change of magnetic flux
• Lenz's law: induced current opposes the change causing it (energy conservation)
• Factors affecting induced EMF: speed of motion, field strength, number of turns

AC Generator

• Parts: rectangular coil, magnets, slip rings, brushes, external circuit
• One complete rotation produces one AC cycle; frequency = rotation rate
• Energy conversion: mechanical energy → electrical energy

Transformer

• Step-up: Vs/Vp = Ns/Np > 1; step-down: Ns/Np < 1
• Ideal transformer: Vp × Ip = Vs × Is (power conserved)
• Core losses (eddy currents, hysteresis) reduce efficiency; laminated core minimises eddy currents

ICSE Exam Tips — Electromagnetism

• Draw and label all diagrams clearly: motor, generator, transformer
• State Faraday's and Lenz's laws correctly in words before formulae
• Common error: confusing slip rings (AC gen) with commutator (DC motor)