Question

A moving coil Galvanometer of resistance $100\, \Omega$ is used as an ammeter using aresistance $0.1\, \Omega$. The maximum deflection current in the Galvanometer is $100\, \mu A$. Find the minimum current in the circuit so that ammeter shows maximum deflection?

• A. $100.1 \,mA$
• B. 1000. 1\, mA$
• C. $10.01 \,mA$
• D. $1.01 \,mA$

Answer 1

Answer: (A)

We are given with following ammeter

Now, $V_{A B}=I_{g} G=\left(I-I_{g}\right) S$
$\left(100 \times 10^{-6}\right) 100=\left(I-100 \times 10^{-6}\right) 0.1$
$I-100 \times 10^{-6}=10^{-1}$
$I=0.1+100 \times 10^{-6}$
$=0.1+0.0001=0.1001\, A=100.1 \,mA$
So, circuit current is $100.1 \,mA$.