Question

An ammeter has a resistance of G ohm and a range of ‘i’ ampere. The value of resistance used in parallel, to convert into an ammeter of range ‘ni’ ampere is

• A. $nG$
• B. $(n-1)G$
• C. $G/n$
• D. $G/(n-1)$

Answer 1

The correct option is D $G/(n-1)$

$V=iR$
$=iG$
Now, a resistance R is connected in parallel to G
So, equivalent resistance $=\frac{RG}{R+G}$
So, with same potential
$V=i_{1}Reqn$
$iG=\left(in\right)\left(\frac{RG}{R+G}\right)$
$R+G=nR$
$R=\frac{G}{n-1}$