Question

The thermo e.m.f. of a thermo-couple is $25\, ?V/^?C$ at room temperature. A galvanometer of $40\, ohm$ resistance, capable of detecting current as low as $10^{-5}\, A$, is connected with the thermocouple. The smallest temperature difference that can be detected by this system is

• A. $16^?C$
• B. $12^?C$
• C. $8^?C$
• D. $20^?C$

Answer 1

Answer: (A)

$16^?C$

Answer 2

$E = 25\, ? ? 10^{-6}\, V$ $IR = 10^{-5} ? 40 = 4 ? 10^{-4}\, V$ $\theta=\frac{4\times10^{-4}}{25\times10^{-6}}=16^{?}C$