In a potentiometer arrangement, a cell of emf $1.20\, V$ gives a balance point at $36\, cm$ length of wire. This cell is now replaced by another cell of emf $1.80\, V$. The difference in balancing length of potentiometer wire in above conditions will be $....cm$.
A$17$
B$18$
C$16$
D$12$
JEE MAIN 2022, Diffcult
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B$18$
b $1.2=($ Potential Gradient $) \times 36$
$1.8=($ Potential Gradient $) \times x$
On dividing, we get
$\frac{2}{3}=\frac{36}{x}$
$x=18 \times 3=54\,cm$
Hence difference $=54-36=18\,cm$
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