Current Electricity

JEE Main level, single correct, medium

379 of 380

Question 379 of 380

The thermo e.m.f. of a thermo-couple is 25μV/∘C25 \mu \mathrm{V} /{ }^{\circ} \mathrm{C} at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as 10−5 A10^{-5} \mathrm{~A}, is connected with the thermo couple. The smallest temperature difference that can be detected by this sytem is

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Answer: (A) 16∘C16^{\circ} \mathrm{C}

ΔT=4025×10−6×10−5⇒ΔT=160C\Delta \mathrm{T}=\frac{40}{25 \times 10^{-6} \times 10^{-5}} \Rightarrow \Delta \mathrm{T}=16^0 \mathrm{C}

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