Question

A milliammeter of range $10 \,mA$ 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-10\, mA ) \times 0.1 $
$\Rightarrow 990\, mA =I-10\, mA$
$ \Rightarrow I=1000 \,mA =1 \,A$