Question

In the DC milli voltmeter circuit shown in figure, the input voltage for full scale deflection is

• A. 10 V
• B. 1 V
• C. 100 mV
• D. 10 mV

Answer 1

The correct option is A 10 V


For full scale deflection,
$I_m=1mA$

Also, Using virtual ground concept,
$V_A=0V$

$\Rightarrow V=10i_1=100i_2$

Also,
$i_1+i_2=1mA$

$\Rightarrow i_1=\frac{10}{11}mA$

$i_2=\frac{1}{11}mA$

Applying KVL in input Loop,

$V_i-V_A=100i_1$

$\Rightarrow V_i=\frac{100}{11}V=9.09V\approx 10V$