Magnetic Effects of Electric Current – Class 10 Physics Chapter 12

Magnetic Effects of Electric Current

Hans Christian Oersted discovered in 1820 that a compass needle deflects when placed near a current-carrying conductor, proving the connection between electricity and magnetism.

Magnetic Field and Field Lines

• A magnetic field is a region around a magnet where its influence can be felt.
• Field lines emerge from the North pole and enter the South pole.
• They never intersect and are closer together where the field is stronger.

Magnetic Field Due to a Current-Carrying Conductor

Straight conductor: Concentric circles around the wire. Direction found using the Right-Hand Thumb Rule: thumb points in the direction of current, curled fingers show the direction of the magnetic field.

Circular loop (coil): The field at the centre is straight and perpendicular to the plane of the loop. Increases with more turns and more current.

Solenoid: A coil of many turns behaves like a bar magnet. The field inside is uniform and strong. An electromagnet is a solenoid with a soft iron core.

Force on a Current-Carrying Conductor in a Magnetic Field

F = BIl (when conductor is perpendicular to field)

Direction of force: Fleming's Left-Hand Rule (Motor Rule)

• Forefinger → Magnetic Field (B)
• Middle finger → Current (I)
• Thumb → Force/Motion (F)

Electric Motor

Converts electrical energy into mechanical energy. Works on Fleming's Left-Hand Rule. Key parts: armature coil, magnets, split-ring commutator, brushes. Used in fans, mixers, washing machines.

Electromagnetic Induction

Michael Faraday discovered that a changing magnetic field in a coil induces an electric current (EMF). This is the principle behind generators.

Fleming's Right-Hand Rule (Generator Rule): Forefinger → Field, Thumb → Motion, Middle finger → Induced current.

Electric Generator

Converts mechanical energy into electrical energy using electromagnetic induction.

• AC Generator: Uses slip rings → produces alternating current (used in power plants)
• DC Generator: Uses split-ring commutator → produces direct current

Domestic Electric Circuits

In India, household supply is 220V AC at 50 Hz. The three wires are: Live (red), Neutral (black), and Earth (green). Fuse and MCB are safety devices that break the circuit during overloading or short-circuiting.

Reference: NCERT Science Textbook for Class 10 – Chapter 12; Concepts of Physics by HC Verma.