Question

A milliammeter of range $10mA$ and resistance $9\Omega$ is joined in a circuit as shown. The metre gives full-scale deflection for current $I$ when $A$ and $B$ are used as its terminals, i.e., current enters at $A$ and leaves at $B$ ( $C$ is left isolated). The value of $I$ is

• A. 100 mA
• B. 900 mA
• C. 1 A
• D. 1.1 A

Answer 1

Answer: (C)

Between $A$ and $B$,
$(9+0.9)\times 10\times 10^{-3}=(I-10mA)\times 0.1$
$\Rightarrow 990mA=I-10mA$
$\Rightarrow I=1000mA=1A$