Thermal Sensors Questions and Answers

Q: The sensitivity of a thermocouple is defined as

The sensitivity is defined as the ratio of output voltage to temperature difference.A thermocouple produces a Seebeck voltage proportional to the temperature difference between its hot and cold junctions. Its sensitivity is the output per degree, dV/dT, quoted in microvolts per degree Celsius. A type K thermocouple, for example, gives about 41 microvolts per degree.The inverse ratio, temperature per volt, is not a sensitivity. The product of the two Seebeck coefficients has no physical meaning here. The difference of the two coefficients is what that ratio works out to for a given pair of metals, but the paper asks for the definition, and the definition is the ratio of output to temperature difference.

Direction for [ Question No: 1 To 1 ] :

Assertion – Reason type questions :
The following items consist of two statements, one labelled the ‘Assertion (A)’ and the other labelled the ‘Reason (R)’. You are to examine these two statements and decide if the Assertion (A) and the Reason (R) are individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answers to these items using the codes given below and mark your answer sheet accordingly.

Codes :
(A) Both (A) and (R) are true and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(C) (A) is true and (R) is false.
(D) (A) is false and (R) is true.

Assertion (A) : Due to two metal with different coefficient of expansion, when the junction is formed, the junction produces a voltage corresponding to temperature.

Reason (R) : The metals which are used for making thermocouples are non homogeneous.

A.Both (A) and (R) are true and (R) is the correct explanation of (A).
B.Both (A) and (R) are true but (R) is not the correct explanation of (A).
C.(A) is true and (R) is false.
D.(A) is false and (R) is true.

Exam Year(s)

UGC NET - 2012,

Answer: B

The key marks both statements as true, but with the reason not explaining the assertion. A thermocouple is made by joining two dissimilar metals, and the junction produces a voltage that depends on the temperature, which is the thermoelectric effect, and that is the content of the assertion in the key. The reason says that the metals used are non homogeneous, meaning that they differ from each other, which is a necessary condition for a thermocouple but does not by itself explain how the voltage is produced. So the two statements are true, but the reason does not explain the assertion. I could not confirm the explanation of the mechanism given in the assertion about the coefficient of expansion, so the answer rests on the official key. The answer is that both are true and (R) is not the correct explanation of (A).

Discuss in Forum

The sensitivity of a thermocouple is defined as

A.Ratio of output voltage to temperature difference
B.Ratio of temperature difference to output voltage
C.Product of Seebeck coefficients of both metals
D.Difference of Seebeck coefficients of both metals

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: A

The sensitivity is defined as the ratio of output voltage to temperature difference.

A thermocouple produces a Seebeck voltage proportional to the temperature difference between its hot and cold junctions. Its sensitivity is the output per degree, dV/dT, quoted in microvolts per degree Celsius. A type K thermocouple, for example, gives about 41 microvolts per degree.

The inverse ratio, temperature per volt, is not a sensitivity. The product of the two Seebeck coefficients has no physical meaning here. The difference of the two coefficients is what that ratio works out to for a given pair of metals, but the paper asks for the definition, and the definition is the ratio of output to temperature difference.

Discuss in Forum

What will be the output of K-type thermocouple at 100 °C ?

A.40 \(\mu\)V
B.400 \(\mu\)V
C.4000 \(\mu\)V
D.4 V

Exam Year(s)

UGC NET - 2012,

Answer: C

The output of a K-type (chromel-alumel) thermocouple at 100 degrees C is about 4.1 mV, relative to a reference junction at 0 degrees C, which is close to 4000 microvolts. The sensitivity of a K-type couple is about 41 microvolts for each degree, so for 100 degrees the figure is roughly 4100 microvolts, and the nearest option is 4000 microvolts. The option of 40 microvolts is about one degree's worth, 400 microvolts is ten degrees' worth and 4 V is a thousand times too big for a thermocouple, whose outputs are in millivolts. The answer is 4000 microvolts.

Discuss in Forum

Which is the most linear temperature transducer ?

A.Thermocouple
B.RTD
C.IC-sensor
D.Thermistor

Exam Year(s)

UGC NET - 2012,

Answer: C

The IC sensor is the most linear temperature transducer, option (C). Integrated circuit sensors such as the AD590 or LM35 are built on the nearly linear dependence of the base-emitter voltage difference of two transistors on absolute temperature, and they give an output of a fixed number of microamperes or millivolts per kelvin. A thermocouple, option (A), has a nonlinear emf and needs tables or a correction. An RTD, option (B), is fairly linear but has a slight curvature. A thermistor, option (D), is strongly nonlinear, being exponential in temperature.

Discuss in Forum

A thermistor is used to measure the temperature. Following characteristics are given

1. They exhibit positive temperature coefficient and poor sensitivity.
2. They exhibit negative temperature coefficient for resistance.
3. Their resistance decreases with the increase in temperature.
4. They are made of oxides of semi conductors. Which one of the following is correct ?

A.1 & 4 only
B.1 & 3 only
C.2, 3 & 4
D.1, 3 and 4

Exam Year(s)

UGC NET - 2014,

Answer: C

The correct statements are 2, 3 and 4. A thermistor is a thermally sensitive resistor made of oxides of semiconductors, with a negative temperature coefficient: its resistance falls as the temperature rises, and it is highly sensitive.

Statement 1 says it has a positive temperature coefficient and poor sensitivity, which is the opposite of the facts for a typical thermistor, so it is false. That removes the options that include statement 1.

Discuss in Forum

Match the following lists of various thermocouples & sensitivity:

List - I	List - II
a. Copper constantan	i. 3-20 µv/°C
b. Chromel/ Alumel	ii. 5-12 µv/°C
c. Tungsten / Tungsten 26% Rhenium	iii. 15-60 µv/°C
d. Platinum / Platinum 10% Rhodium	iv. 40-55 µv/°C

The correct match is : a b c d

A.ii i iii iv
B.iii iv i ii
C.iv i iii ii
D.i ii iii iv

Exam Year(s)

UGC NET - 2014,

Answer: B

The match is a-iii, b-iv, c-i, d-ii. Copper constantan has a sensitivity of 15 to 60 microvolts per degree Celsius, chromel alumel 40 to 55, tungsten against tungsten 26 percent rhenium 3 to 20, and platinum against platinum 10 percent rhodium 5 to 12, since the noble-metal couple is the least sensitive.

The other options give platinum couples the highest sensitivity or copper constantan the lowest, which the ranges do not allow.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Thermal Sensors Questions and Answers || Thermal Sensors MCQ Questions and Answers || Thermal Sensors GK Questions and Answers || Thermal Sensors GK MCQ Questions || Thermal Sensors Multiple Choice Questions and Answers || Thermal Sensors GK || GK on Thermal Sensors || Sensors and Transducers Questions and Answers || Sensors and Transducers MCQ Questions and Answers || Sensors and Transducers GK Questions and Answers || GK on Sensors and Transducers

Thermal Sensors Questions and Answers

Direction for [ Question No: 1 To 1 ] :

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications