CBSE Class 10 Science: Magnetic Effects of Current — Notes 2026

Magnetic Field of Current

• Oersted's experiment: current deflects compass; right-hand thumb rule for straight wire
• Solenoid: coil of wire; magnetic field like bar magnet; strength proportional to current and turns
• Electromagnet: soft iron core in solenoid; temporary magnet; used in cranes, MRI

Force on Current in Magnetic Field

• F = BIL sin θ; Fleming's left-hand rule gives direction
• Torque on current loop: τ = BINA; basis of electric motor
• Application: loudspeaker, electric motor, moving coil galvanometer

Electric Motor

• DC motor: converts electrical energy to mechanical energy
• Parts: rectangular coil, permanent magnet, split-ring commutator, carbon brushes
• Commutator: reverses current every half rotation to maintain continuous rotation

Electromagnetic Induction

• Faraday's experiment: moving magnet near coil induces EMF; changing flux induces current
• Lenz's law: induced current opposes the change causing it
• Factors increasing induced EMF: faster motion, stronger magnet, more coil turns

AC Generator

• Converts mechanical to electrical energy using electromagnetic induction
• Parts: coil, magnetic field, slip rings (not commutator), brushes
• Produces alternating current (AC): direction reverses each half rotation

Transformer

• Works only with AC; based on mutual induction
• Step-up (Ns > Np): increases voltage; step-down (Ns < Np): decreases voltage
• Energy losses: eddy currents (reduced by lamination), hysteresis, resistance of windings

CBSE Exam — Magnetic Effects

• State and explain Fleming's left-hand rule with an example
• Why does AC need a transformer but DC cannot use a transformer?
• Draw a labelled diagram of an AC generator and explain its working