Q. A thermocouple of negligible resistance produces an $e$.m.f. of $40\mu V/℃$ in the linear range of temperature. A galvanometer of resistance $10\ ohm$ whose sensitivity is $1\mu A/div,$ is employed with the thermocouple. The smallest value of temperature difference that can be detected by the system will be
A) $0.1℃$
B) $0.25℃$
C) $0.5℃$
D) $1℃$
Explanation
(b) 1 division $= 1\mu A$
Current for $1℃ = \frac{40\mu V}{10} = 4\mu A$
$1\mu A = \frac{1}{4}\ ℃ = 0.25℃$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.