Question 497: Current Electricity

Question

In an ammeter, $0.25 \%$ of main current passes through the galvanometer. If the resistance of the galvanometer is ' G ', the resistance of ammeter will be

Accepted Answer

$$\begin{aligned}
& \mathrm{I}=\mathrm{I}_{\mathrm{g}}+\mathrm{I}_{\mathrm{s}} \
& \mathrm{I}=\frac{0.25 \mathrm{I}}{100}+\mathrm{I}_{\mathrm{s}} \
& \mathrm{I}_{\mathrm{s}}=\frac{399}{400} \mathrm{I} \quad	ext{.... (i)}\
& \mathrm{I}_{\mathrm{g}} \mathrm{G}=\mathrm{I}_{\mathrm{s}} \mathrm{~S} \
& \mathrm{~S}=\frac{0.25}{100} 	imes \frac{400}{399} 	imes \mathrm{G} \quad	ext{.... [From (i)]}\
& \mathrm{~S}=\frac{1}{399} \mathrm{G}\quad	ext{.... (ii)}
\end{aligned}$$
$$
\begin{aligned}
&	ext { Total resistance of ammeter }\
&\begin{aligned}
R & =\frac{G S}{G+S} \
& =\frac{G\left(\frac{1}{399} Gight)}{\left(G+\frac{1}{399} Gight)} \quad	ext{... [From (ii)]}\
& =\left(\frac{\frac{1}{399}}{\frac{400}{399}}ight) \mathrm{G}\
R & =\frac{1}{400} G
\end{aligned}
\end{aligned}$$

Answer

$\frac{399}{400} \mathrm{G}$

Answer

$\frac{1}{400} \mathrm{G}$

Answer

$\frac{499}{500} \mathrm{G}$

Answer

$\frac{1}{500} \mathrm{G}$

Current Electricity

In an ammeter, 0.25 \% of main current passes through the galvanometer. If the resistance of the galvanometer is ' G ', the resistance of ammeter will be

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