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प्रश्न
The potentiometer wire AB shown in the figure is 50 cm long. When AD = 30 cm, no deflection occurs in the galvanometer. Find R.
उत्तर
It is given that at point D, there is no deflection in the galvanometer, i.e. the bridge is balanced
\[\Rightarrow \frac{R_{AD}}{R_{DB}} = \frac{6}{R}\]
According to the principle of a potentiometer,
\[\frac{R_{AD}}{R_{DB}} = \frac{l_{AD}}{l_{DB}}\]
\[ \Rightarrow \frac{6}{R} = \frac{30}{20}\]
\[ \Rightarrow R = \frac{20 \times 6}{30} = 4 \Omega\]
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