To know the resistance G of a galvanometer by half deflection method, a battery of emf VE and resistance R is used to deflect the galvanometer by angle θ. If a shunt of resistance S is needed to get half deflection then G, R and S are related by the equation :
2S (R + G) = RG
S ( R + G) = RG
2S = G
2G = S
As we learnt in
Moving coil galvanometer -
It is a very sensitive instrument used to measure the small current.Galvanometer gives the deflection which is proportional to electric current flowing through it.
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From Ohm's Law
where, Ig = Galvanometer Current
G = Galvanometer resistance
When shunt of resistance s is connected parallel to the galvanometer then
After calculate, we get
RG = S(R+G)
Option 1)
2S (R + G) = RG
This is incorrect option.
Option 2)
S ( R + G) = RG
This is correct option.
Option 3)
2S = G
This is incorrect option.
Option 4)
2G = S
This is incorrect option.
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