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Magnetic Effects of Electric Current

Introduction

     Major progress in understanding magnetism came after Hans Christian Oersted established the relationship between electricity and magnetism in 1820.

Magnetic Field and Field Lines

     Magnetic field is a region near a magnetised body where magnetic forces can be detected.

Mapping of Magnetic Lines of Force

     A pictorial representation that gives the direction of the magnetic field at various points in a magnetic field is called a map of the magnetic field.

Magnetic Field Lines Due to a Current in a Straight Conductor

     We need to understand the pattern of field lines around a straight conductor carrying current and also the direction of these field lines.

Rules for Determining the Direction of Magnetic Field

     The direction of magnetic field around a current carrying conductor can be determined by using one of the laws.

Magnetic Field due to a Current Carrying Circular Loop

     The demonstration given below explains the nature of magnetic field due to a current carrying circular loop.

Rule for Determining the Direction of Magnetic Field in a Coil Carrying Current

     If a coil carrying current is suspended by thin elastic long conductors, it will align itself as the compass needle.

Magnetic Field Due to a Solenoid

     A solenoid is a long coil (shaped like a cylinder) containing a large number of close turns of insulated copper wire.

Electromagnet

     An electromagnet can be defined as a soft-iron core that is magnetised temporarily by passing a current through a coil of wire wound on the core.

Force Acting on a Current-Carrying Conductor in a Magnetic Field

     Oersted's experiment shows that a current carrying wire exerts a force on a magnetic needle and deflects it from its usual north-south position.

Principle and Working of Electric Motor

     An electric motor is a device which converts electrical energy into mechanical energy. A common motor works on direct current. So, it is also called DC motor.

Induced Current and Magnetic Field

     The deflection is more if the magnet is moved faster. That is, the rate at which the current is induced is more when the magnet is moved faster.

Mutual Induction

     The phenomenon of production of induced emf in one coil due to change of current in a neighbouring coil is called mutual induction.

Electric Generator (AC)

     When a straight conductor is moved rapidly in a magnetic field, then a current is induced in the conductor. It is based on the phenomenon of electromagnetic induction.

Direct and Alternating Current

     When the current flows in the same direction it is called 'direct current' or DC.The current derived from a cell or battery is unidirectional. So it is a DC source.

Domestic Electric Circuits

     Electric power is usually generated at places which are far away from the places where it is consumed. At the generating station, the electric power is generated at 11,000 volts. This voltage alternates at a frequency of 50 Hz.

Electric Fuse

     When the electrical appliance is switched on, the metal casing of the appliance will remain at zero potential as it is in contact with the earth wire in the three pin socket. It thus prevents us from an electric shock even if we touch it accidentally.

Summary

     The phenomenon by which an emf or current is induced in a conductor due to change in the magnetic field near the conductor is known as electromagnetic induction.


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Multiple Choice Questions

     



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