A thermocouple of negligible resistance produces an e.m.f. of 40 µV/⁰C in the linear range of temperature. A galvanometer of resistance 10 ohm whose sensitivity is 1 µA/div, is employed with the thermocouple. The smallest value of temperature difference that can be detected by the system will be

Options

(a) 0.5⁰C
(b) 1⁰C
(c) 0.1⁰C
(d) 0.25⁰C

Correct Answer:

0.25⁰C

Explanation:

I division = 1µA
Current for 1⁰C = 40µV / 10 = 4µA
1µA = 1/4 ⁰C = 0.25⁰C