Question

A thermo couple develops 40 μV/kelvin. If hot and cold junctions be at 40^oC and 20^oC respectively then the emf develops by a thermopile using such 150 thermo couples in series shall be

• A. 150 Mv
• B. 80 Mv
• C. 80 Mv
• D. 120 Mv

Answer 1

Answer: (D)

120 Mv

Answer 2

The temperature difference is 20⁰C = 20 K. So that thermo emf developed E = aθ $= 40\frac{\mu V}{K} \times 20K = 800\mu V.$

Hence total emf = 150 × 800 = 12 × 10⁴ μV = 120 Mv