Engineering :: Instrumentation and Process Control

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41.

The pressure thermometer bulb should have a

A.	large area	B.	large mass
C.	large specific heat	D.	low thermal conductivity

42.

Vapour pressure thermometers work on the principle of

A.	increase of vapour pressure with decrease in temperature	B.	increase of vapour pressure with increase in temperature
C.	volumetric expansion of vapour with increase in temperature	D.	increase in electric resistance with increase in temperature

43.

Thermocouples use two

A.	dissimilar metal wires	B.	similar metal wires
C.	similar metal strips	D.	dissimilar metal strips

44.

The generation of e.m.f. in thermocouples is fundamentally explained by

A.	Ohms law	B.	Stefan-Boltzmans law
C.	Seebeck effect	D.	Joule heating effect.

45.

Which one of the following thermocouples develops least e.m.f. for the same difference of temperature between hot and cold junctions?

A.	Iron-constantan	B.	Copper-constantan
C.	Chromel-alumel	D.	Platinum-platium + 13% rhodium

46.

Peltier effect relates

A.	absorption and evolution of heat at the junctions of a thermocouple to the current flow in the circuit	B.	e.m.f. generated in a single homogeneous wire and the temperature difference
C.	electrical resistance with temperature	D.	e.m.f. generated in a single homogeneous wire and the temperature difference

47.

Thomson effect relates

A.	absorption and evolution of heat at the junctions of a thermocouple to the current flow in the circukt	B.	electrical resistance with temperature
C.	e.m.f. generated in a single homogeneous wire and the temperature difference

48.

For a given thermocouple e.m.f. generated

A.	depends on the tempaterature of hot junction	B.	depends on the temperature of cold junction
C.	depends on the temperature difference between hot and cold junctions	D.	is constant for all temperature differences between hot and cold junctions

49.

The generation of e.m.f. in thermocouples is fundamentally explained by

A.	Seebeck effect	B.	Peltier effect
C.	Thomson effect	D.	all of the above.

50.

Which one of the following properties of thermocouples for industrial use is undersirable?

A.	Relative large thermal e.m.f.	B.	Resistance to corrosion and oxidation
C.	Non-linear relation of e.m.f. to temperature	D.	Precision of calibration