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The emf of the driver cell of a potentiometer is 2V and its internal resistance is negligible. The length of the potentiometer wire is 100cm and the resistance is 5 $\Omega$ . How much resistance (in $\Omega$ ) is to be connected in series with the potentiometer to have a potential gradient of 0.05mV/cm?
Option: 1
1995

Option: 2
2000

Option: 3
1990

Option: 4
2095

Answers (1)

best_answer

Potential gradient K= $\frac{V}{l}=0.05mV/cm$

$=5mV/m$

$I=\frac{K.l}{r}=\frac{5*10^{-3}*1}{5}= 10^{-3}A$

$Now\: \: 2=I(R+r)$

or $2=10^{-3}(R+5)\: \: or\: \: R=1995\Omega$

Posted by

sudhir.kumar

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