MCQ
A moving coil galvanometer has $150$ equal divisions. Its current sensitivity is $10$ divisions per milliampere and voltage sensitivity is $2$ divisions per millivolt. In order that each division reads $1$ volt, the resistance in ohms needed to be connected in series with the coil will be
  • A
    $99995\ \Omega$
  • $9995 \ \Omega$
  • C
    $10^3$
  • D
    $10^5$

Answer

Correct option: B.
$9995 \ \Omega$
$ \text { Voltage sensitivity }=\frac{\text { Current sensitivity }}{\text { Resistance of galvanomet er G }}$
$ \Rightarrow G=\frac{10}{2}=5 \Omega .$
Here $i_g=$ Full scale deflection current $=\frac{150}{10}=15 \mathrm{~mA}$.
$V=$ Voltage to be measured $=150 \times 1=150\mathrm{~V}$.
Hence $R=\frac{V}{i_g}-G=\frac{150}{15 \times 10^{-3}}-5=9995\  \Omega$.

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