Concepts Of Physics MCQ Edition [Volume 2]PhysicsThermal and Chemical Effects of Electric Current
The junction temperatures of a bismuth–silver thermocouple are kept at 0^ C and 0.001^ C . Determine the developed thermo-emf (Seebeck emf). Given for bismuth–silver, a = -46 10⁻⁶ V ^ C⁻¹ and b = -0.48 10⁻⁶ V ^ C⁻² .
Options
- A-2.3 10⁻⁸ V
- B4.6 10⁻⁸ V
- C-4.6 10⁻⁶ V
- D-4.6 10⁻⁸ V
Correct answer
D. -4.6 10⁻⁸ V
Step-by-step solution
The thermo-emf E developed in a thermocouple when the cold junction is at 0^ C and the hot junction is at T^ C is given by the relation: E = aT + 1 2 bT^2 Given: a = -46 10⁻⁶ V ^ C ⁻¹ b = -0.48 10⁻⁶ V ^ C ⁻² T = 0.001^ C = 10⁻³ ^ C Substituting the values into the formula: E = (-46 10⁻⁶)(10⁻³) + 1 2 (-0.48 10⁻⁶)(10⁻³)^2 E = -46 10⁻⁹ - 0.24 10⁻¹² Since the second term is negligibly small compared to the first term, it can be ignored: E -46 10⁻⁹ V E = -4.6 10⁻⁸ V