how can a galvanometer be converted into voltmeter and ammeter
Answers
Ammeter is an electrical measuring device, which is used to measure electric current through the circuit. It is the modified form of galvanometer
CONNECTION OF AMMETER IN CIRCUIT
An ammeter is always connected in series to a circuit.
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CONVERSION OF GALVANOMETER
INTO AMMETER
Since Galvanometer is a very sensitive instrument therefore it can’t measure heavy currents. In order to convert a Galvanometer into an Ammeter, a very low resistance known as "shunt" resistance is connected in parallel to Galvanometer. Value of shunt is so adjusted that most of the current passes through the shunt. In this way a Galvanometer is converted into Ammeter and can measure heavy currents without fully deflected.
VALUE OF SHUNT RESISTANCE
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Let resistance of galvanometer = Rg and it gives full-scale deflection when current Ig is passed through it. Then,
Vg = IgRg -------(i)
Let a shunt of resistance (Rs) is connected in parallel to galvanometer. If total current through the circuit is I.

Then current through shunt:
Is = (I-Ig)
potential difference across the shunt:
Vs= IsRs
or
Vs = (I – Ig)Rs -------(ii)
But
Vs =Vg
(I - Ig)Rs = IgRg

VOLT METER
Voltmeter is an electrical measuring device, which is used to measure potential difference between two points in a circuit.
CONNECTION OF VOLTMETER IN CIRCUIT
Voltmeter is always connected in parallel to a circuit.
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CONVERSION OF GALVANOMETER INTO VOLTMETER
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Since Galvanometer is a very sensitive instrument, therefore it can not measure high potential difference. In order to convert a Galvanometer into voltmeter, a very high resistance known as "series resistance" is connected in series with the galvanometer.
VALUE OF SERIES RESISTANCE
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Let resistance of galvanometer = Rg and resistance Rx (high) is connected in series to it. Then combined resistance = (Rg + Rx).

If potential between the points to be measured = V and if galvanometer gives full-scale deflection, when current "Ig" passes through it. Then,
V = Ig (Rg + Rx)
V = IgRg + IgRx
V – IgRg = IgRx
Rx = (V – IgRg)/Ig

Thus Rx can be found.
Galvanometer into Ammeter
Galvanometer can be connected to a low resistance called stunt resistence in parallel to convert galvanometer in to ammeter.
Galvanometer into Voltmeter
Galvanometer can be connected to a high resistance called multipier in series to convert galvanometer in to voltmeter.