Question

An ammeter gives full scale deflection with a current of $1amp$. It is converted into an ammeter of range $10amp$. The ratio of the resistance of ammeter to the shunt resistance used will be :

• A. $1:9$
• B. $1:10$
• C. $1:11$
• D. $9:1$

Answer 1

The correct option is D $9:1$

An ammeter gives full scale deflection with a current of 1 amp $r_1=\frac{V}{1}=V$.

ammeter of range $r_2=\frac{V}{10}=0.1V$.

The ratio of the resistance of ammeter to the shunt resistance used

$\frac{r_1}{r_2}=\frac{V-0.1V}{0.1V}=\frac{0.9V}{0.1}=9:1$