Question

A multimeter of a range 10 mA has a coil of resistance 1$\Omega$ . to use it as an ammeter of range 1 A, the required shunt must have a resistance of :

• A. $\frac{1}{101}\Omega$
• B. $\frac{1}{100}\Omega$
• C. $\frac{1}{99}\Omega$
• D. $\frac{1}{9}\Omega$

Answer 1

The correct option is C $\frac{1}{99}\Omega$

An ammeter in connected in this form :-

Given Range of multimeter,

$Ig=10mA$

voltage across Resistor $R_s$ and Multimeter

$RgIg=R_s(I-Ig)=V$

so, we get , $R_s=\frac{RgIg}{(I-Ig)}$

putting values,

$R_s=\frac{1\times 0.01}{1-0.01}=\frac{0.01}{0.99}=\frac{1}{99}\Omega$