CBSE – 10th Standard Science

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Class 10 Chapter 13 – Magnetic Effects of Electric Current

  • Magnetic Effects of Electric Current
    • An electric current-carrying wire behaves like a magnet. Thus we can say that electricity and magnetism are linked to each other.
    • Hans Christian Oersted, played a crucial role in understanding electromagnetism.
    • The unit of magnetic field strength is named the Oersted in his honor.
    • The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field

    MAGNETIC FIELD AND FIELD LINES

    • The lines along which the iron filings align themselves represent magnetic field lines.
    • Magnetic field is a quantity that has both direction and
    • The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.

    MAGNETIC FIELD DUE TO A CURRENT-CARRYING CONDUCTOR

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    • The magnetic field produced by a given current in the conductor decreases as the distance from it increases.
    • The concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it
    • At every point of a current-carrying circular loop, the concentric circles representing the magnetic field.
    • By the time we reach at the centre of the circular loop, the arcs of these big circles would appear as straight lines.

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    • The magnetic field produced by a circular coil having n turns, the field produced is in times as large as that produced by a single turn.
    • A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a

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    • The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
    • The direction of the force on the conductor depends upon the direction of current and the direction of the magnetic field
    • According to Fleming’s left-hand rule stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular If the first finger points in the direction of magnetic field
    • An electric motor is a rotating device that converts electrical energy to mechanical energy.

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    • The commercial motors use an electromagnet in place of permanent magnet, large number of turns of the conducting wire in the current carrying coil; and a soft iron core on which the coil is wound, is called an armature.
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    • Michael Faraday. In 1831, Faraday discovered that a moving magnet can be used to generate electric currents.
    • A potential difference is induced in the secondary coil whenever the electric current through the primary coil is changing starting or stopping
    • As the current in the first coil changes, the magnetic field associated with it also changes
    • The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field
    • If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor, then the middle finger will show the direction of induced current. This simple rule is called Fleming’s right-hand rule.

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    • Fleming’s right-hand rule is also employed to produce large currents for use in homes and industry.
    • In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. the working of a split ring commutator in the case of an electric motor
    • Thus a unidirectional current is produced. The generator is thus called a DC generator. Current, which changes direction after equal intervals of time, is called an alternating current This device is called an AC generator.
    • The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.
    • An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.
    • A fuse in a circuit prevents damage to the appliances and the circuit due to overloading.
    • A compass needle is a small magnet.
    • The phenomenon of electromagnetic induction is the production of induced current in a coil placed in a region where the magnetic field changes with time.
    • A generator converts mechanical energy into electrical energy. It works on the basis of electromagnetic induction.

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    • In our houses we receive AC electric power of 220 V with a frequency of 50 Hz.
    • Earth wire and Fuse is the most important safety device  measure to ensure that any leakage of current to a metallic body does not give any severe shock to a user.

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