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Question: Answered & Verified by Expert
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
PhysicsCurrent ElectricityJEE MainJEE Main 2003
Options:
  • A
    $16^{\circ} \mathrm{C}$
  • B
    $12^{\circ} \mathrm{C}$
  • C
    $8^0 \mathrm{C}$
  • D
    $20^{\circ} \mathrm{C}$
Solution:
2676 Upvotes Verified Answer
The correct answer is:
$16^{\circ} \mathrm{C}$
$\Delta \mathrm{T}=\frac{40}{25 \times 10^{-6} \times 10^{-5}} \Rightarrow \Delta \mathrm{T}=16^0 \mathrm{C}$

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