Q. The thermo emf of copper-constantan couple is $40\mu$V per degree. The smallest temperature difference that can be detected with this couple and a galvanometer of 100$\Omega$ resistance capable of measuring the maximum current of $1\mu$A is
A) 10$℃$
B) 7.5$℃$
C) 5.0$℃$
D) 2.5$℃$
Explanation
(d) If $T$ is the smallest temperature difference that can be detected, then
$40 \times 10^{- 6}T = 100 \times 10^{- 6}$
$\Rightarrow T = 2.5℃$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.