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# The length of a wire of a potentiometer is 100 cm and the e.m.f. of its standard cell is E volt

The length of a wire of a potentiometer is 100 cm and the e.m.f. of its standard cell is E volt. It is employed to measure the e.m.f. of a battery whose internal resistance is 0.5$\Omega$ If the balance point is obtained at l=30 cm from the positive end, the e.m.f. of the battery is

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Using the principle of potentiometer $v\alpha l$

$\frac{V}{E}= \frac{l}{L}\: \: or\: \: V=\frac{l}{L}E= \frac{30E}{100}$

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