Process Control & Instrumentation Mcqs for Chemical - Set 15

1)   Thermistors which have a very high temperature co-efficient of resistivity belong to the class of solid called________________?

a. Dielectrics
b. Insulators
c. Semi conductors
d. Conductors
Answer  Explanation 

ANSWER: Semi conductors

Explanation:
No explanation is available for this question!


2)   What is the Laplace transform of sin t ?

a. 1/(s2 + 1)
b. s/(1 + s2)
c. 1/(s2 – 1)
d. s/(s2 – 1)
Answer  Explanation 

ANSWER: 1/(s2 + 1)

Explanation:
No explanation is available for this question!


3)   Silver point temperature is ______________ °C?

a. 760.5
b. 860.5
c. 960.5
d. 1060.5
Answer  Explanation 

ANSWER: 960.5

Explanation:
No explanation is available for this question!


4)   A first order system with unity gain and time constant η is subjected to a sinusoidal input of frequency w = 1/η. The amplitude ratio for this system is______________?

a. 0
b. 0.5
c. 1/√2
d. 0.25
Answer  Explanation 

ANSWER: 1/√2

Explanation:
No explanation is available for this question!


5)   Water is flowing through a series of four tanks and getting heated as shown in figure. It is desired to design a cascade control scheme for controlling the temperature of water leaving the tank 4 as there is a disturbance in the temperature of a second stream entering the tank 2. Select the best place to take the secondary measurement for the second loop?

a. Tank 1
b. Tank 2
c. Tank 3
d. Tank 4
Answer  Explanation 

ANSWER: Tank 3

Explanation:
No explanation is available for this question!


6)   Which of the following is not suitable for measuring the temperature of a red hot object in the range of 800 – 1600°C ?

a. Optical pyrometer
b. Radiation pyrometer
c. Photoelectric pyrometer
d. Thermocouples
Answer  Explanation 

ANSWER: Thermocouples

Explanation:
No explanation is available for this question!


7)   Pyrometry refers to the measurement of temperature_________________?

a. With the mercurial thermometer upto 350°C
b. Directly
c. Which is of higher magnitude
d. All A., B. & C.
Answer  Explanation 

ANSWER: Which is of higher magnitude

Explanation:
No explanation is available for this question!


8)   Ordinary mercury in glass thermometer is used for measuring temperature upto 120°C. However, for measuring higher temperature upto __________ °C, thermometer is made by filling nitrogen under pressure above the mercury, which stops the evaporation of mercury and reduces the chance of broken thread of mercury?

a. 250
b. 350
c. 550
d. 700
Answer  Explanation 

ANSWER: 550

Explanation:
No explanation is available for this question!


9)   According to Bode stability criterion, a system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at frequency for which phase lag is_________________?

a.
b. 45°
c. 90°
d. 180°
Answer  Explanation 

ANSWER: 180°

Explanation:
No explanation is available for this question!


10)   Mcleod gauge measures the _____________ pressure?

a. Positive
b. Sub-atmospheric
c. Very high
d. Atmospheric
Answer  Explanation 

ANSWER: Sub-atmospheric

Explanation:
No explanation is available for this question!


11)   Continuous measurement of moisture content of paper in paper industry is done by measuring the_________________?

a. Thermal conductivity through the paper
b. Electrical resistance through the paper
c. Magnetic susceptibility
d. None of these
Answer  Explanation 

ANSWER: Electrical resistance through the paper

Explanation:
No explanation is available for this question!


12)   Liquid column manometers are used for measuring the pressure ______________ kgf/cm2?

a. > 2 (gage)
b. < 3 (gage)
c. < 10 (gage)
d. < atmospheric
Answer  Explanation 

ANSWER: < 3 (gage)

Explanation:
No explanation is available for this question!


13)   Which is the strongest paramagnetic gas ?

a. CO2
b. O2
c. NO
d. NO2
Answer  Explanation 

ANSWER: O2

Explanation:
No explanation is available for this question!


14)   Maximum differential pressure in liquid manometer is ______________ psi?

a. 20
b. 30
c. 40
d. 50
Answer  Explanation 

ANSWER: 30

Explanation:
No explanation is available for this question!


15)   Which of the following instruments is not used for measuring sub-zero (<0°) temperatures ?

a. Platinum resistance thermometer
b. Mercury in glass thermometer
c. Vapor pressure thermometer
d. Radiation pyrometer
Answer  Explanation 

ANSWER: Radiation pyrometer

Explanation:
No explanation is available for this question!


16)   Which of the following cannot measure a temperature of 1600°C ?

a. Platinum resistance thermometer
b. Thermocouple
c. Photo-electric pyrometer
d. Radiation pyrometer
Answer  Explanation 

ANSWER: Platinum resistance thermometer

Explanation:
No explanation is available for this question!


17)   In a second order under damped system, the_________________?

a. Time required for the response of first reach its ultimate value is called the response time
b. Overshoot (which is a measure of how much the response exceeds the ultimate value) increase with the decrease of damping co-efficient
c. Decay ratio (which is the ratio of the sizes of successive peaks) is equal to the reciprocal of overshoot
d. None of these
Answer  Explanation 

ANSWER: Overshoot (which is a measure of how much the response exceeds the ultimate value) increase with the decrease of damping co-efficient

Explanation:
No explanation is available for this question!


18)   “A control system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at the crossover frequency.” This is _______________ criterion?

a. Bode stability
b. Nyquist
c. Routh stability
d. None of these
Answer  Explanation 

ANSWER: Bode stability

Explanation:
No explanation is available for this question!


19)   A typical example of a physical system with under damped characteristic is a____________________?

a. U-tube manometer
b. Spring loaded diaphragm valve
c. CSTR with first order reaction
d. Thermocouple kept immersed in a liquid filled thermowell
Answer  Explanation 

ANSWER: Spring loaded diaphragm valve

Explanation:
No explanation is available for this question!


20)   In a closed loop system, the process to be controlled is an integrating process with transfer function 1/2s. The controller proposed to be used in an integral controller with transfer function 1/T1s. When a step change in set point is applied to such a closed loop system, the controlled variable will exhibit__________________?

a. Overdamped response
b. Underdamped response
c. Undamped response
d. Unstable response
Answer  Explanation 

ANSWER: Underdamped response

Explanation:
No explanation is available for this question!