A potentiometer wire of length 300,cm is conn | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(D) Let the resistance of the potentiometer wire be $R$.The current $i$ flowing through the potentiometer wire is given by $i = \frac{4}{R + 780}$.The

Vedclass · Accepted Answer

$20$

Vedclass · Answer

(D) Let the resistance of the potentiometer wire be $R$.The current $i$ flowing through the potentiometer wire is given by $i = \frac{4}{R + 780}$.The potential difference across the entire potentiometer wire $AB$ is $V_{AB} = iR = \frac{4R}{R + 780}$.The potential gradient along the wire is $k = \frac{V_{AB}}{L} = \frac{4R}{(R + 780) 	imes 300}$.The null point is obtained at a length $l = 60\,cm$ for a cell of emf $E = 20\,mV = 20 	imes 10^{-3}\,V$.At the null point,the potential difference across the length $l$ is equal to the emf of the cell:$E = k 	imes l$$20 	imes 10^{-3} = \left( \frac{4R}{(R + 780) 	imes 300} ight) 	imes 60$Simplifying the equation:$20 	imes 10^{-3} = \frac{4R 	imes 60}{(R + 780) 	imes 300}$$0.02 = \frac{4R}{5(R + 780)}$$0.1(R + 780) = 4R$$0.1R + 78 = 4R$$3.9R = 78$$R = \frac{78}{3.9} = 20\,\Omega$.

Similar Questions

Sensitivity of a potentiometer can be increased by:

In the potentiometer experiment shown in the figure,for the position $X$ of the jockey $J$,there occurs a null deflection in the galvanometer. Then the potential difference between points $A$ and $X$ is ................ $V$.

$A$ battery of $6\,V$ is connected to the terminals of a $3\,m$ long wire of uniform thickness and resistance of the order of $100\,\Omega$. The difference of potential between two points separated by $50\,cm$ on the wire will be .......... $V$.

$A$ potentiometer wire has length $10\, m$ and resistance $20\,\Omega$. $A$ $2.5\, V$ battery of negligible internal resistance is connected across the wire with an $80\,\Omega$ series resistance. The potential gradient on the wire will be

Vedclass Test Series

Exam Paper Generator

Online Exam Module