Ammeter is a device used to measure current in a circuit. It is connected in series with the circuit. The introduction of ammeter should not alter the pd or current in the circuit. Ideally there should be no potential drop across the ammeter. Hence an ideal ammeter has zero resistance.
A galvanometer can be converted into an ammeter by connecting a low resistance in parallel with it.
Let the maximum safe current through a galvanometer of resistance G is Ig and current I is flowing through the circuit. Then the purpose of shunt is to provide a short cut path for I-Ig current without affecting the galvanometer.
However the pd across the galvanometer and the shunt will be one and the same.
pd across shunt=pd across galvanometer.
ie, (I-Ig)S=IgG
S=Ig/(I-Ig)G
Thus a galvanometer of resistance G and maximum safe current Ig can be converted into an ammeter to read a maximum current of I by connecting a shunt of values =Ig/(I-Ig)G across it..
A galvanometer can be converted into an ammeter by connecting a low resistance in parallel with it.
Let the maximum safe current through a galvanometer of resistance G is Ig and current I is flowing through the circuit. Then the purpose of shunt is to provide a short cut path for I-Ig current without affecting the galvanometer.
However the pd across the galvanometer and the shunt will be one and the same.
pd across shunt=pd across galvanometer.
ie, (I-Ig)S=IgG
S=Ig/(I-Ig)G
Thus a galvanometer of resistance G and maximum safe current Ig can be converted into an ammeter to read a maximum current of I by connecting a shunt of values =Ig/(I-Ig)G across it..
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