The resistance of $10\, metre$ long potentiometer wire is $1\,ohm/meter$. A cell of $e.m.f.$ $2.2\, volts$ and a high resistance box are connected in series to this wire. The value of resistance taken from resistance box for getting potential gradient of $2.2\, millivolt/metre$ will be ............... $\Omega $
Medium
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(c) Potential gradient $x = \frac{V}{L} = \frac{e}{{(R + {R_h} + r)}} \cdot \frac{R}{L}$
$ \Rightarrow $ $2.2 \times {10^{ - 3}} = \frac{{2.2}}{{(10 + {R_h})}} \times 1$
$ \Rightarrow $ $R' = 990\,\Omega $
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