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Introduction |
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Major progress in understanding magnetism came after Hans Christian Oersted established the relationship between electricity and magnetism in 1820. |
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Magnetic Field and Field Lines |
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Magnetic field is a region near a magnetised body where magnetic forces can be detected. |
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Mapping of Magnetic Lines of Force |
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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. |
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Magnetic Field Lines Due to a Current in a Straight Conductor |
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We need to understand the pattern of field lines around a straight conductor carrying current and also the direction of these field lines. |
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Rules for Determining the Direction of Magnetic Field |
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The direction of magnetic field around a current carrying conductor can be determined by using one of the laws. |
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Magnetic Field due to a Current Carrying Circular Loop |
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The demonstration given below explains the nature of magnetic field due to a current carrying circular loop. |
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Rule for Determining the Direction of Magnetic Field in a Coil Carrying Current |
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If a coil carrying current is suspended by thin elastic long conductors, it will align itself as the compass needle. |
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Magnetic Field Due to a Solenoid |
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A solenoid is a long coil (shaped like a cylinder) containing a large number of close turns of insulated copper wire. |
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Electromagnet |
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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. |
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Force Acting on a Current-Carrying Conductor in a Magnetic Field |
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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. |
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Electric Motor |
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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. |
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Electromagnetic Induction |
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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. |
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Mutual Induction |
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The phenomenon of production of induced emf in one coil due to change of current in a neighbouring coil is called mutual induction. |
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Electric Generator (AC) |
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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. |
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Direct and Alternating Current |
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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. |
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Domestic Electric Circuits |
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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. |
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Electric Fuse |
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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. |
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Summary |
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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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Question and Answers |
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Multiple Choice Questions |
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