Question
Tue April 17, 2012 By:

# can you give the symbols used in a circuit diagram and a description about the galvanomtre ,voltmetre etc if any

Expert Reply
Tue April 17, 2012

 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 Â– Ig)Rs -------(ii) But Vs =Vg(I - Ig)Rs = IgRg

 oltmeter is always connected in parallel to a circuit. SYMBOL CONVERSION OF GALVANOMETER INTO VOLTMETER www.citycollegiate.com 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 www.citycollegiate.com 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 Â– IgRg = IgRx Rx = (V Â– IgRg)/Ig
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