Heat Transfer MCQ’s – Response of a Thermocouple
1 - Question
“The response of a thermocouple is defined as the time required for the thermocouple to reach the surrounding temperature when it is exposed to it”.
Explanation: It is the source temperature.
2 - Question
The sensitivity of thermocouple is defined as the time required by thermocouple to reach how much percentage of its steady state values?
Explanation: The time constant of a thermocouple represents the time required to attain 63.2% value.
3 - Question
The response time for different sizes and materials of thermocouple wires usually lie between
a) 0.04 to 2.5 seconds
b) 0.06 to 1.2 seconds
c) 0.02 to 0.04 seconds
d) 2.4 to 9.4 seconds
Explanation: Depending upon the type of fluid used, the response time for different sizes and materials of thermocouple wires usually lie between o.o4 to 2.5 seconds.
4 - Question
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for time required by the thermocouple to reach 197 degree Celsius temperature. Assume the thermos-physical properties as given below k = 20 W/ m K h = 350 W/m2 K c = 0.4 k J/kg K p = 8000 kg/m3
a) 1.094 seconds
b) 2.094 seconds
c) 3.094 seconds
d) 4.094 seconds
Explanation: It doesn’t consist of an ammeter.
5 - Question
For what purpose we use thermometric well?
a) To measure current
b) To measure resistance
c) To measure temperature of gas
d) To stop heat dissipation
Explanation: We use this apparatus for the measurement of a temperature of gas flowing through pipeline.
6 - Question
In thermometric well, the error can be minimized by (i) The value of parameter ml slows down by some quantity. (ii) Lagging of the tube so that conduction of heat along its length is arrested.
Explanation: Here, we increase the value of parameter ml.
7 - Question
Suppose there are two reservoirs A and B. Let TA and TB be the temperatures of respective reservoirs. At any instant say TA = TB. In this case, maximum temperature occurs at
d) All over the rod
Explanation: Here temperatures are same so x = ½ i.e. middle of the rod.
8 - Question
The relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures are
a) α = α 1 at x = 0 and α = α 2 at x = infinity
b) α = α 1 at x = 1 and α = α 2 at x = 2L
c) α = α 1 at x = infinity and α = α 2 at x = 1
d) α = α 1 at x = 0 and α = α 2 at x = L
Explanation: It should be at x = o and x = L.
9 - Question
“The tube that is used in a thermometric well is considered as a hollow fin and the temperature distribution is obtained by using the relation applicable to infinitely long fin”.
Explanation: The relation applicable to fin with insulated tip is used here.
10 - Question
"The diameter of well does not have any effect on temperature measurement by the thermometer”.
Explanation: Here, there is no relation between well diameter and temperature.