First slide

potentiometer

Question

A cell of emf 10 volt and internal resistance $2 Ω$ gives a null point in a potentiometer and the balancing length is found to be 55 cm. Now the cell is short circuited through an external resistance. R and the balancing length is found to be 50 cm then the value of R is

Moderate

A

40 $Ω$
B

20 $Ω$
C

30 $Ω$
D

25 $Ω$

Solution

$r = R (\frac{l_{1}}{l_{2}} - 1)$
$∴ R = \frac{2}{(\frac{55}{50} - 1)} Ω = 20 Ω$

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