Q. A cell having emf of 1.5V, when connected across a resistance of 14$\ \Omega$, produces a voltage of only 1.4V across this resistance. The internal resistance of the cell must be
A) 1$\ \Omega$
B) 14$\ \Omega$
C) 15$\ \Omega$
D) 21$\ \Omega$
Explanation
(a) Internal resistance of the cell
$r = \left\lbrack \frac{E}{V} - 1 \right\rbrack R\ $
$r = \left\lbrack \frac{1.5}{1.4} - 1 \right\rbrack 14 = 1\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.