First slide

potentiometer

Question

The e.m.f. of the driver cell of a potentiometer is 2V and its internal resistance is negligible. The length of the potentiometer wire is 100 cm and resistance is 5 $Ω$ . How much resistance is to be connected in series with the potentiometer wire to have a potential gradient of $0.05 m v c m^{- 1}$

Moderate

A

$1990 Ω$
B

$2000 Ω$
C

$1995 Ω$
D

None of these

Solution

$\begin{array}{l} ε = 2 V, l = 100 c m R_{p} = 5 Ω \\ V / L = 0.05 m V / c m \\ \frac{V}{L} = (\frac{E}{R_{P} + R_{S}}) \frac{R_{P}}{L} \end{array}$
Substituting and solving
$R_{S} - 1995 Ω$

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