Explain how a moving coil galvanometer is converted into voltmeter. Derive the necessary formula.
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=) A voltmeter is made by connecting a resistor of high resistance R in series with a privoted-type moving-coil galvanometer G ( In figure ) . The value of R depends upon the range of the required voltmeter and can be calculated as follows :-
Let G be the resistance of the coil of the galvanometer and Ig the current which , on passing through the galvanometer , produces full-scale deflection . Suppose , V is the maximum p.d. to the measured which exists between two points a and b in a circuit . On connecting the galvanometer across the points a and b in , a current Ig flows through it . Then , we have
Ig = V / G + R
G + R = V / Ig
R = ( V / Ig ) - G
If the current Ig in the coil produces a full-scale deflection , then for the potential difference V between the points a and b there will be a full-scale deflection . Thus , on connecting resistance R of the above value in series with the galvanometer , the galvanometer will become a voltmeter of range 0 to V volt . For the voltmeter , a high resistance is connected in series with the galvanometer and so the resistance of a voltmeter is very high compared to that of a galvanometer .
____________________________
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HOPE , IT HELPS ... ✌️
__________________________
__________________________
=) A voltmeter is made by connecting a resistor of high resistance R in series with a privoted-type moving-coil galvanometer G ( In figure ) . The value of R depends upon the range of the required voltmeter and can be calculated as follows :-
Let G be the resistance of the coil of the galvanometer and Ig the current which , on passing through the galvanometer , produces full-scale deflection . Suppose , V is the maximum p.d. to the measured which exists between two points a and b in a circuit . On connecting the galvanometer across the points a and b in , a current Ig flows through it . Then , we have
Ig = V / G + R
G + R = V / Ig
R = ( V / Ig ) - G
If the current Ig in the coil produces a full-scale deflection , then for the potential difference V between the points a and b there will be a full-scale deflection . Thus , on connecting resistance R of the above value in series with the galvanometer , the galvanometer will become a voltmeter of range 0 to V volt . For the voltmeter , a high resistance is connected in series with the galvanometer and so the resistance of a voltmeter is very high compared to that of a galvanometer .
____________________________
____________________________
HOPE , IT HELPS ... ✌️
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