The thermo e.m.f. of a thermo-couple is 25 μ 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 thermo couple. The smallest temperature difference that can be detected by this sytem is

Correct answer: (A) 16^° C. Δ T=frac4025 × 10^-6 × 10^-5 ⇒ Δ T=16^0 C

Q158 / 225 · JEE Main 2003 · Physics

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

$\Delta \mathrm{T}=\frac{40}{25 \times 10^{-6} \times 10^{-5}} \Rightarrow \Delta \mathrm{T}=16^0 \mathrm{C}$

Hence, the correct answer is option: 'A'.