A thermocouple of negligible resistance produces an emf fo `40 mu V//^(@)C` in the linear range of temperature. A galvanometer of resistance `10 Omega` 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

Options

A. `0.5^(@)C`
B. `1^(@)C`
C. `0.1^(@)C`
D. `0.25^(@)C`

Answer

D

Explanation

(d) For minimum deflection of 1 divison require current `= 1 mu A`
Voltage required `= iR = 1 xx 10 = 10 mu V`
`:. 40 mu V~= 1 ^(@)C`
`10 mu V ~= (1)/(4)^(@)C`
`= 2.50^(@)C`