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Question
A galvanometer of resistance 100 Ω gives a full-scale deflection for a potential difference of 200 mV.
- What must be the resistance connected to convert the galvanometer into an ammeter of the range 0-200 mA?
- Determine resistance of the ammeter.
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Solution
(i) Given: G = 100 Ω; I = 200 mA;
Vg = 200 mV;
Resistance to be connected to the galvanometer to convert to an ammeter:
S = `("I"_"g""G")/(("I"-"I"_"g"))`
Here Ig= `("V"_"g")/"G"`
= `(200 " mV")/(100 " Ω")`
= 2 mA
S = `(2 × 10^(-3) × 100)/((0.2-0.002))`
S = 1.01 Ω
(ii) `1/"R" = 1/100 + 1/1.01`
R = 0.999 Ω
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