In a given thermocouple, the neutral temperature : (a) is a constant (b) depends on the temperature of cold ju

Question 59 of 102

Q. In a given thermocouple, the neutral temperature :

(a) is a constant

(b) depends on the temperature of cold junction

(d) both

(b) and (c)

Tamil Nadu DgeTamil Nadu HSC (DGE) Board 2017MCQ· 1mImportance★★★★★

58% · 59/102 Questions

🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

The neutral temperature of a thermocouple is an intrinsic constant of the metal pair, unaffected by the cold-junction temperature; it is the temperature of inversion that shifts with the cold junction.

In a thermocouple, as the hot-junction temperature is raised (with the cold junction held at some fixed reference temperature $T_c$ ), the thermo-EMF first increases, reaches a maximum at a particular hot-junction temperature called the neutral temperature $T_n$ , and then decreases — eventually reversing sign at a still higher temperature called the temperature of inversion $T_i$ .

The neutral temperature $T_n$ is determined entirely by the thermoelectric properties (the Seebeck coefficients as functions of temperature) of the particular pair of metals forming the thermocouple — it is where the thermoelectric power $\dfrac{d\varepsilon}{dT}$ becomes zero, a condition set purely by the materials involved. Experimentally and theoretically, $T_n$ is found to be independent of the cold-junction temperature $T_c$ : however cold or warm the reference (cold) junction is kept, the EMF still peaks at the same hot-junction temperature $T_n$ for a given metal pair. This is why $T_n$ is treated as a constant characteristic of the thermocouple.

By contrast, the temperature of inversion $T_i$ (where the EMF becomes zero and reverses) does depend on the cold-junction temperature, related by the standard relation

$T_n = \frac{T_c + T_i}{2}, \quad \text{i.e.} \quad T_i = 2T_n - T_c.$ …

Start your 14-day free trial to unlock the full solution →

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2017Set ANNUAL1 markMCQ
$Q. In a given thermocouple, the neutral temperature :$
(a) is a constant
(b) depends on the temperature of cold junction
(c) depends upon the temperature of inversion
(d) both
(b) and (c)
›Reveal solutionSolution

The neutral temperature of a thermocouple is an intrinsic constant of the metal pair, unaffected by the cold-junction temperature; it is the temperature of inversion that shifts with the cold junction.

In a thermocouple, as the hot-junction temperature is raised (with the cold junction held at some fixed reference temperature $T_c$ ), the thermo-EMF first increases, reaches a maximum at a particular hot-junction temperature called the neutral temperature $T_n$ , and then decreases — eventually reversing sign at a still higher temperature called the temperature of inversion $T_i$ .

The neutral temperature $T_n$ is determined entirely by the thermoelectric properties (the Seebeck coefficients as functions of temperature) of the particular pair of metals forming the thermocouple — it is where the thermoelectric power $\dfrac{d\varepsilon}{dT}$ becomes zero, a condition set purely by the materials involved. Experimentally and theoretically, $T_n$ is found to be independent of the cold-junction temperature $T_c$ : however cold or warm the reference (cold) junction is kept, the EMF still peaks at the same hot-junction temperature $T_n$ for a given metal pair. This is why $T_n$ is treated as a constant characteristic of the thermocouple.

By contrast, the temperature of inversion $T_i$ (where the EMF becomes zero and reverses) does depend on the cold-junction temperature, related by the standard relation

$T_n = \frac{T_c + T_i}{2}, \quad \text{i.e.} \quad T_i = 2T_n - T_c.$ …

Start your 14-day free trial to see the full solution →

←Previous question · 2.8Q14 — In a potentiometer arrangement, a cell of emf 1.25 V gives a balance p…→Next questionQ2 — The colour code of a carbon resistor is, Brown, Black, Brown and Red. …

Q.In a given thermocouple, the neutral temperature :

Concept understanding — Thermoelectric Effects (Seebeck, Peltier, Thomson)

Q.In a given thermocouple, the neutral temperature :

🎓Unlock everything free for 14 days

Unlock everything free for 14 days