A galvanometer has a resistance of 25  Ω and a maximum of 0.01 A current can be passed through it. In order to change it into an ammeter of range 10 A, the shunt resistance required is

# A galvanometer has a resistance of $25\text{\hspace{0.17em}\hspace{0.17em}}\Omega$ and a maximum of 0.01 A current can be passed through it. In order to change it into an ammeter of range 10 A, the shunt resistance required is

1. A

$5/999\text{\hspace{0.17em}\hspace{0.17em}}\Omega$

2. B

$10/999\text{\hspace{0.17em}\hspace{0.17em}}\Omega$

3. C

$20/999\text{\hspace{0.17em}\hspace{0.17em}}\Omega$

4. D

$25/999\text{\hspace{0.17em}\hspace{0.17em}}\Omega$

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### Solution:

$\begin{array}{l}{\mathrm{i}}_{\mathrm{g}}=\mathrm{i}\text{\hspace{0.17em}\hspace{0.17em}}\frac{\mathrm{S}}{\mathrm{G}+\mathrm{S}}\text{\hspace{0.17em}\hspace{0.17em}}⇒\text{\hspace{0.17em}\hspace{0.17em}}0.01=10\text{\hspace{0.17em}}\frac{\mathrm{S}}{25+\mathrm{S}}\\ ⇒\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}1000\text{\hspace{0.17em}\hspace{0.17em}}\mathrm{S}=25+\mathrm{S}\text{\hspace{0.17em}\hspace{0.17em}}⇒\text{\hspace{0.17em}\hspace{0.17em}}\mathrm{S}=\frac{25}{999}\text{\hspace{0.17em}}\mathrm{\Omega }\end{array}$  Register to Get Free Mock Test and Study Material

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