A first order system with a time constant of 1 min is subjected to frequency res

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Question
A first order system with a time constant of 1 min is subjected to frequency response analysis. At an input frequency of 1 radian/min, the phase shift is
Options
A. 45�
B. -90�
C. -180�
D. -45�

Correct Answer

-45�

Process Control and Instrumentation problems

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1. Emf generated in a thermocouple depends on the temperature
Options
A. of cold junction only.
B. of hot junction only.
C. difference between hot and cold junctions.
D. difference between cold junction and atmospheric temperature.

3. Thermal conductivity based continuous flue gas analyser makes use of varying thermal conductivity of the constituents of flue gases. Which of the following constituents of flue gases has the maximum thermal conductivity?
Options
A. CO₂
B. N₂
C. O₂
D. CO

5. Water is entering a storage tank at a temperature T₀ and flow rate Q₀ and leaving at a flow rate Q and temperature T. There are negligible heat losses in the tank. The area of cross-section of the tank is A₀. The model that describes the dynamic variation of temperature of water in the tank with time is given as :
Options
A. Q₀(T₀ - T) = A_c .
B. Q₀T₀ - QT = A_c .
C. Q(T₀ - T) = A_c .
D. Q(T₀ - T) = A_c .

6. A system with a double pole at the origin is unstable since the corresponding term in the time domain
Options
A. is a constant.
B. grows exponentially with time.
C. grows linearly with time.
D. decays linearly with time.

7. A photo electric device in which the resistance of the metal is directly proportional to the light striking on it, is known as photo-conductive cell. Photoelectric transducers are used for the measurement of those parameters, which can be used to produce variation in
Options
A. light intensity
B. current
C. flux density
D. voltage

9. Radiation thermometer can not measure the temperature
Options
A. inside a pressure vessel.
B. of an object without coming in contact with it.
C. of liquid oxygen.
D. of moving objects at high temperature.

10. Thermal wells are used in the temperature measurement to
Options
A. guard against corrosive and oxidising action on thermocouple materials
B. reduce measuring lag.
C. increase the fidelity.
D. increase the sensitivity.

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