{"id":5267,"date":"2024-06-29T00:21:08","date_gmt":"2024-06-29T00:21:08","guid":{"rendered":"https:\/\/vartmaaninstitutesirsa.com\/?page_id=5267"},"modified":"2024-06-29T00:24:17","modified_gmt":"2024-06-29T00:24:17","slug":"moving-coil-galvanometer","status":"publish","type":"page","link":"https:\/\/vartmaaninstitutesirsa.com\/index.php\/moving-coil-galvanometer\/","title":{"rendered":"Moving coil Galvanometer"},"content":{"rendered":"
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Moving coil Galvanometer<\/span><\/u><\/strong><\/h1>\n

Moving coil Galvanometer:-<\/span><\/u><\/strong>\u00a0m.imp<\/sup><\/span><\/u><\/strong><\/h2>\n

A<\/span><\/em>\u00a0Galvanometer is a device which is used to detect the current in a circuit<\/span>.<\/span><\/em><\/p>\n

Principle:-<\/span><\/u><\/p>\n

The Galvanometer is based on the principal that a current carrying coil placed in external magnetic field experience a torque<\/span><\/em>.<\/span><\/p>\n

Construction:-<\/span><\/u> –<\/p>\n

A moving coil Galvanometer consist of<\/span><\/p>\n<\/div>\n

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  1. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 A coil PQRS consist of a large number of turns of fine insulated copper wire wounded over a non magnetic metallic frame. The coil is suspended from a movable torsion head H by mean of a fine phosphor bronze strip. The lower end of coil is connected to fine spiral spring S\u2019. An arrangement of strong north & South Pole is fixed on both sides of the coil.<\/li>\n
  2. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 A soft iron core L of spherical or cylindrical shape is placed between the coils.<\/li>\n
  3. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0A circular Mirror M is attached to the Phosphor bronze strip, to measure the deflection of the coil.<\/li>\n
  4. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0The torsion head is connected to a binding terminal T1<\/sub><\/span> & spring S\u2019 is connected to another binding terminal T2<\/sub><\/span>.<\/li>\n<\/ol>\n

    Theory:-<\/span><\/u><\/p>\n

    Let N is number turns in coil, A is area of coil, B is magnetic field I is the amount of current following through the coil, then torque acting on the coil is\u00a0<\/span><\/p>\n

    \"\"<\/p>\n

    Here \u03b8 is angle between normal to the plane of coil & applied magnetic field.<\/span><\/p>\n

    Since the field is\u00a0<\/span>radial<\/span><\/strong><\/p>\n

    i,e<\/span>\u03b8 = 90<\/span>0\u00a0<\/sup><\/span>\"\"<\/p>\n

    \"\"<\/p>\n

    Due to this torque the phosphor bronze wire suffer twist, if \u03b8 is angle of twist & k is moment of restoring couple per unit angular twist then moment of restoring couple = k \u03b8<\/span><\/p>\n

    In equilibrium<\/span><\/p>\n

    \"\"<\/p>\n

    Or<\/span>\"\"<\/p>\n

    Here\u00a0<\/span>\"\"\u00a0= K = a another constant\u00a0<\/span><\/p>\n

    So<\/span>I\u00a0<\/span><\/strong>\"\"\u00a0\u03b8<\/span><\/strong><\/p>\n

    Hence current through the coil is directly proportional to the deflection of the coil.<\/span><\/em><\/p>\n

    Sensitivity of a moving coil Galvanometer<\/span><\/u><\/strong><\/h3>\n

    A galvanometer is said to be more sensitive if it show large deflection even for a small change in current is passed through it.<\/span><\/p>\n

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    1. Current sensitivity: – it is defined as the deflection produced in the galvanometer when a unit current is passed through it.<\/li>\n<\/ol>\n

      I,e.\u00a0<\/span>Current sensitivity<\/span><\/p>\n

      \"\"<\/p>\n

        \n
      1. Voltage sensitivity: – It is defined as the deflection produced in the galvanometer when a unit potential difference is applied across it.<\/li>\n<\/ol>\n

        Voltage sensitivity <\/span>V<\/span>s<\/sub><\/span>=<\/span>\"\"=<\/span>\"\"<\/p>\n

        =<\/span>\"\"<\/p>\n

        Clearly voltage sensitivity =<\/span>\"\"<\/p>\n

        The sensitivity of a moving coil galvanometer can be increased by\u00a0<\/span><\/em><\/p>\n

        \uf0fc<\/span>By increasing number of turns in the coil.<\/span><\/p>\n

        \uf0fc<\/span>By increasing the magnetic field.<\/span><\/p>\n

        \uf0fc<\/span>By increasing the area of the oil.<\/span><\/p>\n

        \uf0fc<\/span>By decreasing the value of torsion constant R<\/span><\/p>\n

        Advantage of moving coil Galvanometer:-<\/span><\/u><\/p>\n