For full scale deflection of total 50 divisions, 50 mV voltage is required in a galvanometer. The resistance of galvanometer for its current sensitivity of 2 div/ mA would be-
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 2 Ω
Current sensitivity is the deflection per unit current, so it gives the current needed for full-scale deflection. The resistance then follows from Ohm’s law with the full-scale voltage.
\( \displaystyle I_g = \frac{\text{number of divisions}}{\text{current sensitivity}} = \frac{50\,\mathrm{div}}{2\,\mathrm{div\,mA^{-1}}} \)
\( \displaystyle I_g = 25\,\mathrm{mA} = 25\times10^{-3}\,\mathrm{A} \)
\( \displaystyle G = \frac{V}{I_g} = \frac{50\times10^{-3}\,\mathrm{V}}{25\times10^{-3}\,\mathrm{A}} \)
\( \displaystyle G = 2\,\Omega \)