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    Ballistic Galvanometer S1

    Uploaded by

    Saurabh Yadav
    1) The document describes experiments to determine the charge sensitivity (ballistic constant K) and critical damping resistance (CDR) of a ballistic galvanometer. 2) To find K, a known standard capacitor is fully charged and then discharged through the galvanometer, allowing K to be calculated from the capacitance, voltage, and deflection. 3) To find CDR, resistance is gradually increased in the galvanometer circuit until the damping changes the motion from oscillatory to non-oscillatory, defining the critical damping.

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    © All Rights Reserved
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    Ballistic Galvanometer S1

    Uploaded by

    Saurabh Yadav
    2K views18 pages
    1) The document describes experiments to determine the charge sensitivity (ballistic constant K) and critical damping resistance (CDR) of a ballistic galvanometer. 2) To find K, a known standard capacitor is fully charged and then discharged through the galvanometer, allowing K to be calculated from the capacitance, voltage, and deflection. 3) To find CDR, resistance is gradually increased in the galvanometer circuit until the damping changes the motion from oscillatory to non-oscillatory, defining the critical damping.

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    1) The document describes experiments to determine the charge sensitivity (ballistic constant K) and critical damping resistance (CDR) of a ballistic galvanometer. 2) To find K, a known standard capacitor is fully charged and then discharged through the galvanometer, allowing K to be calculated from the capacitance, voltage, and deflection. 3) To find CDR, resistance is gradually increased in the galvanometer circuit until the damping changes the motion from oscillatory to non-oscillatory, defining the critical damping.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    2K views18 pages

    Ballistic Galvanometer S1

    Uploaded by

    Saurabh Yadav
    1) The document describes experiments to determine the charge sensitivity (ballistic constant K) and critical damping resistance (CDR) of a ballistic galvanometer. 2) To find K, a known standard capacitor is fully charged and then discharged through the galvanometer, allowing K to be calculated from the capacitance, voltage, and deflection. 3) To find CDR, resistance is gradually increased in the galvanometer circuit until the damping changes the motion from oscillatory to non-oscillatory, defining the critical damping.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 18

    CHARGE SENSITIVITY & C.D.R.

    OF BALLISTIC GALVANOMETER

    Kirori Mal College

    By – Shubham Gupta (2030117) &


    Saurabh Yadav(2030154)
    BALLISTIC GALVANOMETER -

    A ballistic galvanometer is a type of sensitive galvanometer; commonly a mirror galvanometer.


    Unlike a current-measuring galvanometer, the moving part has a large moment of inertia, thus
    giving it a long oscillation period. It is really an integrator measuring the quantity
    of charge discharged through it. It can be either of the moving coil or moving magnet type.

    Before
      first use the ballistic constant of the galvanometer must be determined. This is usually
    done by connecting to the galvanometer a known capacitor, charged to a known voltage, and
    recording the deflection. The constant K is calculated from the capacitance C, the voltage V and
    the deflection d: 

    K=      
    where K is expressed in coulombs per centimeter.
    In operation the unknown quantity of charge Q (in coulombs) is simply: 

    Q = Kd      
    CHARGE SENSITIVITY -

    Charge sensitivity of the ballistic galvanometer is defined as the charge in micro- coulombs
    which when sent through the coil will produce a deflection of 1 mm of the spot on the scale
    placed at a distance of 1 metre from the galvanometer mirror.
    AIM -

    To determine the Charge sensitivity (or the Ballistic Constant K) of a Ballistic


    Galvanometer using a standard Capacitor of known Capacitance.

    Apparatus -

    A moving coil Ballistic Galvanometer, a lamp and scale arrangement, a cell, a


    standard Capacitor of known Capacitance (0.1 μF ), a voltmeter, a Morse key, a
    tapping key and connecting wires.
    THEORY -
    When a Capacitor of Capacitance C is charged fully to known potential
    difference V, the charge on it is given by
    Q = CV

    The  fully charged Capacitor is now discharged through the Ballistic


    Galvanometer whose constant K is to be determined. If is the first corrected


    throw of the galvanometer, then
    Q = CV = K
    hence K=
    PROCEDURE -
     Level the Ballistic Galvanometer and see that its coil moves freely. Keep the lamp and
    scale arrangement at a distance of 1 metre from the Galvanometer mirror and get a spot
    on zero of the scale.

     Make the connections as in Fig. Rh is a rheostat and C is a Capacitor of known


    capacitance. K is the Morse key and is a tapping key.
      

     Make the connections between a and c by pressing the Morse key K. The capacitor C will
    get charged. Release the morse key, connection is made between c and b and the capacitor
    discharges through B.G. If the deflection goes out of scale or is too small, adjust the
    potential with the help of rheostat so that on pressing the morse key and then releasing it
    a full scale deflection is obtained.
     Change the Voltage V by changing the sliding contact of the rheostat and repeat the experiment to take
    5 – 6 such observations.

     Bring the spot of light to rest with the help of the tapping key . Release and press the morse key K,
      release it and note down the first throw and the second throw on the same side. Note the voltage V
    across the Capacitor.
    Corrected throw
    Pot. diff. across the First throw Second throw
    S.No. Capacitor V (Volts) (cm) (cm) = (cm)

    1.
    2.

    3.

    4.

    5.
    6.
    OBSERVATIONS –
    Capacitance of the capacitor C = ……μF.

    Calculations –
      
    The Ballistic constant or the charge sensitivity is given by
    K=

    A graph between the potential drop V across c along X-axis and the corrected deflection along
    Y – axis.
    The graph will be a straight line with slope =
    THEN K=

    = ……..MICROCOULOMB/CM
     
    =…….MICROCOULOMB/MM

    Result –

    The Ballistic constant K of the Ballistic Galvanometer =


    …………microcoulomb/mm.
    AIM -

    To determine the Critical Damping Resistance(CDR) of a Ballistic Galvanometer .

    APPARATUS –

    A moving coil Ballistic Galvanometer, a lamp and scale arrangement, a cell of constant
    Emf ,3 resistance boxes , a one way key , a reversing key, a tapping key and
    connecting wires.
    THEORY-

    An oscillatory system can be rendered dead beat by suitably increasing damping.


    The amount of damping at which transition from oscillatory to dead beat condition takes place is known as
    critical damping. In this moment moving part of galvanometer quickly comes to rest.
    The value of total resistance in the galvanometer circuit at which critically damped condition is achieved is
    known as Critical Damping Resistance(CDR).
    When resistance in the galvanometer circuit is larger than CDR , galvanometer becomes oscillatory and
    when it is smaller than CDR it is dead beat .
    PROCEDURE -

     Make connection as in Fig. Take out a large resistance from Q and R and a small resistance
    from P. Take out a large resistance from R and start the current . The coil will be found to
    oscillate before coming to rest. If the spot of light goes off the scale , decrease P or Q , till the
    spot remains on the scale.
     Decrease R in suitable steps. The coil becomes less and less oscillatory. For certain value of
    R, it will be found that the spot of light does not just overshoot its position of rest. Thus the
    galvanometer is set for CDR.
     The critical damping resistance CDR = ( P+R+G) ohms where G is the galvanometer resistance. Here
    (P+R) is called the external CDR or the external critical damping resistance.
    Results –
      

    The Critical Damping Resistance of the ballistic galvanometer = ……… Ω


    References –
     BSC Practical Physics by Geeta Sanon.
     Wikipedia.org
     Brainly.in
    THANK YOU

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    18

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