Define the current sensitivity of a galvanometer. Write its S.I. … - Vidyadip

Question

Define the current sensitivity of a galvanometer. Write its S.I. unit.
Figure shows two circuits each having a galvanometer and a battery of 3 V. When the galvanometers in each arrangement do not show any deflection, obtain the ratio R₁/ R₂.

✓

Answer

Ratio of deflection produced in the galvanometer to the current flowing through it.
Current sensitivity $\text{S}_{i} = \frac{\theta}{\text{I}}$
S.I. unit of current sensitivity S_i is division/ampere or radian/ampere.
For balanced Wheatone bridge, if no current flows through the galvanometer
$\frac{4}{\text{R}_{1}} = \frac{6}{9}\Rightarrow\text{R}_{1} = \frac{4\times9}{6} =6\Omega$
For another current
$\frac{6}{12} = \frac{\text{R}_{2}}{8}\Rightarrow\text{R}_{2} = \frac{6\times8}{12} = 4\Omega$
$\therefore\frac{\text{R}_{1}}{\text{R}_{2}} = \frac{6}{4} = \frac{3}{2}.$

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