Question

A moving coil galvanometer has following characteristics. Number of turns of coil $=80$; Area of coil $=50m{m}^2$; Resistance of coil $=20\Omega$; Flux density of radial field $0.2T$; Torsional constant of suspension wire $=5\times 10^{-9}Nm/rad$. For this moving coil galvanometer, mark the correct statement(s).

• A. The angular deflection produced due to a potential difference of $0.01mV$ is $0.08$ div.
• B. Current sensitivity of the device is $160div/mA$.
• C. Voltage sensitivity of the device is $8div/mV$.
• D. All of these.

Answer 1

Answer: (D)

Current sensitivity
$I_S=\frac{\theta }{I}=\frac{BAN}{k}=\frac{0.2\times 50\times 10^{-6}\times 80}{5\times 10^{-9}}$ div/amp
$=160\times 10^3$ div/amp $=160$ div / mA
Voltage sensitivity, $V_S=\frac{\theta }{V}=\frac{BAN}{kR}=\frac{I_S}{R}$
$=8$ div / mV
For $V=0.01mV,\theta =8\times 0.01=0.08$ div