Short Summary

Chapter 13, Magnetic Effects of Electric Current, explains magnetic fields, electromagnetism, electromagnetic induction, and domestic electric circuits. Hans Christian Oersted discovered that electric currents produce magnetic fields, and magnetic field lines form continuous closed curves, running from the North pole to the South pole outside a magnet and from South to North inside it, while never intersecting one another. The magnetic field around a straight current-carrying conductor consists of concentric circles, with its direction determined by the Right-Hand Thumb Rule. A current-carrying solenoid produces a nearly uniform magnetic field inside it similar to that of a bar magnet, and placing a soft iron core inside the solenoid produces an electromagnet. A current-carrying conductor placed in a magnetic field experiences a force, which is maximum when the conductor is perpendicular to the magnetic field, and the direction of this force is determined by Fleming’s Left-Hand Rule. Electric motors use this force along with a split-ring commutator to convert electrical energy into mechanical energy. Michael Faraday discovered electromagnetic induction, in which an electric current is produced when the magnetic field around a conductor changes, and the direction of the induced current is determined by Fleming’s Right-Hand Rule. Electric generators work on this principle to convert mechanical energy into electrical energy. Alternating current (AC) periodically reverses its direction and has a frequency of 50 Hz in India, making it suitable for low-loss transmission of electricity over long distances, while direct current (DC) flows in one direction. Domestic electric circuits in India operate at a potential difference of 220 V and use live, neutral, and earth wires, conventionally coloured red, black, and green respectively, with the earth wire providing protection against electric shocks.