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Moving Charges and Magnetism — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsMoving Charges and Magnetism3 Marks
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 $R_{1 }/ R_2.$
✓

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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