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Multiple choice question for engineering

Set 1

1. Which of the following is not a type of radiation detectors?
a) Geiger Muller counter
b) Proportional counter
c) Semiconductor detector
d) Flame emission detector

View Answer

Answer: d [Reason:] Flame emission detector is not a type of radiation detector. Radiation can be detected by several methods.

2. ‘When nuclear radiations pass through, gas ionization is produced.’ This is the principle of which of the following detectors?
a) Proportional counter
b) Flow counter
c) Geiger Muller counter
d) Scintillation counter

View Answer

Answer: c [Reason:] ‘When nuclear radiations pass through, gas ionization is produced.’ This is the principle of which of Geiger Muller counter. It is used to measure the intensity of radioactive radiation.

3. Which of the following acts as quenching gas in Geiger Muller counter?
a) Alcohol
b) Argon gas
c) Krypton
d) Hydrogen

View Answer

Answer: a [Reason:] Alcohol acts as quenching gas in Geiger Muller counter. It is present in a gas tight envelope along with the electrodes.

4. Which of the following acts as ionising gas in Geiger Muller counter?
a) Alcohol
b) Argon gas
c) Krypton
d) Hydrogen

View Answer

Answer: b [Reason:] Argon gas acts as ionising gas in Geiger Muller counter. It is present in a gas type envelope along with the electrodes.

5. Which of the detectors is similar to Geiger Muller counter in construction but is filled with heavier gas?
a) Proportional counter
b) Flow counter
c) Semiconductor detector
d) Scintillation counter

View Answer

Answer: a [Reason:] Proportional counter is similar to Geiger Muller counter in construction but is filled with heavier gas. The output is proportional to the intensity of radiation incident on it.

6. Which of the following gases are used in proportional counter as the ionising gas?
a) Alcohol
b) Argon gas
c) Krypton
d) Hydrogen

View Answer

Answer: c [Reason:] Proportional counter is filled with krypton. It acts as ionising gas. Xenon can also be used.

7. Which of the following is the main disadvantage of solid state semiconductor detector?
a) Low accuracy
b) Low sensitivity
c) It should be maintained at low temperature
d) High pressure has to be produced

View Answer

Answer: c [Reason:] The main disadvantage of solid state semiconductor detector is that it must be maintained at low temperature. This is necessary to reduce noise and to prevent deterioration of detector characteristics.

8. Scintillation detector is a large flat crystal of which of the following materials?
a) Sodium chloride
b) Sodium iodide
c) Sodium sulphate
d) Sodium carbonate

View Answer

Answer: a [Reason:] Scintillation detector is a large flat crystal of sodium iodide. It is coated with thallium doping.

9. When X-ray enters the solid state detector it produces ion pair rather than electron-hole pair.
a) True
b) False

View Answer

Answer: b [Reason:] When X-ray enters the solid state detector it produces electron-hole pair rather than ion pair. The output signal is taken from an aluminium layer.

10. Which of the following materials are used as the insulation between inner and outer electrodes of the ion chamber?
a) Polythene
b) Plastic
c) Polytetrafluoroethylene
d) Polyacrylamide

View Answer

Answer: c [Reason:] Polytetrafluoroethylene is used as the insulation between inner and outer electrodes of the ion chamber. The material has very high resistance.

11. Liquid samples must be counted using ionization chamber by placing them in which of the following?
a) Test tube
b) Curvette
c) Ampoules
d) Flask

View Answer

Answer: c [Reason:] Liquid samples must be counted using ionization chamber by placing them in ampoules. The ampoules are placed in the chamber.

12. Gaseous compounds containing radioactive sources can be directly introduced into the ionization chamber.
a) True
b) False

View Answer

Answer: a [Reason:] Gaseous compounds containing radioactive sources can be directly introduced into the ionization chamber. Liquid samples cannot be introduced directly.

13. Liquid Scintillators are used for which of the following materials?
a) Low energy beta materials
b) High energy beta materials
c) Low energy gamma materials
d) High energy gamma materials

View Answer

Answer: a [Reason:] Liquid Scintillators are used for low energy beta materials. Solid scintillators are used for high energy beta materials.

14. Given below is the block diagram of proportional counter. Identify the unmarked component.
analytical-instrumentation-questions-answers-radiation-detectors-q14
a) Collimator
b) Detector crystal
c) Pre-amplifier
d) Position logic circuit

View Answer

Answer: c [Reason:] The unmarked component is pre-amplifier. There are two amplifiers namely pre-amplifier and main amplifier.

15. Given below is a diagram of Scintillation detector. Identify the unmarked component.
analytical-instrumentation-questions-answers-radiation-detectors-q15
a) Lens
b) Collimator
c) Dynodes
d) Focussing cup

View Answer

Answer: c [Reason:] The unmarked components are dynodes. Scintillation detector is a combination of scintillator and photo multiplier tube.

Set 2

1. Which of the following is placed just before the detector in radiofrequency mass
spectrometer?
a) Ion source
b) Potential energy selector
c) Ionisation chamber
d) Reflectron

View Answer

Answer: b [Reason:] A potential energy selector is placed before the detector. It balances out the energy of the ion beam.

2. Which of the following is applied in one or more stages where each stage is a series of three equally spaced parallel grids?
a) Ionisation field
b) Reflection
c) RF field
d) Acceleration

View Answer

Answer: c [Reason:] RF field is applied in one or more stages. Each stage is a series of three equally spaced parallel grids.

3. The alternating voltage rf voltage is applied to which of the following?
a) All grids
b) Central grid
c) Alternate grids
d) None of the grids

View Answer

Answer: b [Reason:] The alternating voltage rf voltage is applied to the central grid. All the other grids are kept at ground potential.

4. The rf spectrometer contains a magnet.
a) True
b) False

View Answer

Answer: b [Reason:] Rf spectrometer does not contain a magnet. Rf field is applied for this type of mass spectrometer.

5. The DC ion accelerating voltage is swept from _________
a) 0 to 50 V
b) 50 to 100 V
c) 200 to 300 V
d) 50 to 250 V

View Answer

Answer: d [Reason:] The DC ion accelerating voltage is swept from 50 to 250 V. This is done twice per second.

6. The resolution of the Bennet tube can be improved by using which of the following?
a) Sine wave rf signal
b) Square wave rf signal
c) Triangular wave rf signal
d) Random signal

View Answer

Answer: b [Reason:] The resolution of the Bennet tube can be improved by using square wave rf signal. Usually, sinusoidal wave signal is used.

7. In Bennet spectrometer, the rf voltage has a fixed frequency.
a) True
b) False

View Answer

Answer: a [Reason:] In Bennet spectrometer, the rf voltage has a fixed frequency. It is modulated at 10 percent at 1kHz.

8. The spurious lines can be reduced to minimum by using which of the following?
a) Single stage tube
b) Two stage tube
c) Three stage tube
d) Reflectron

View Answer

Answer: c [Reason:] The spurious lines can be reduced to minimum by using three stage tubes. Two stage tubes tend to produce spurious lines.

9. Which of the following is the disadvantage of using three stage tubes?
a) Reduced resolution
b) Bulky construction
c) Complex
d) Heavy

View Answer

Answer: a [Reason:] The spurious lines can be reduced to minimum by using three stage tubes. This results in reduced resolving power.

10. Which of the following is not the feature of Bennet type spectrometer?
a) Lightweight
b) Simple
c) Absence of spurious lines
d) Moderate resolution

View Answer

Answer: c [Reason:] Absence of spurious lines is not a feature of Bennet type spectrometer. Spurious lines can be reduced by adding new features.

11. The resolving power of Bennet type spectrometer is primarily based on which of the following?
a) Distance between detector and reflectron
b) Difference between the individual rf accelerating stages
c) Length of the drift tube
d) Laser beam used

View Answer

Answer: b [Reason:] The resolving power of Bennet type spectrometer is primarily based on difference between the individual rf accelerating stages.

Set 3

1. Which of the following cannot be used as secondary reference electrode?
a) Calomel electrode
b) Silver-silver chloride electrode
c) Mercury-mercury sulphate electrode
d) Glass electrode

View Answer

Answer: d [Reason:] Glass electrode cannot be used as secondary reference electrode. It is an indicator electrode. It responds to the changes in the activity of the analyte ion.

2. Which of the following is known as calomel?
a) Silver chloride
b) Mercury chloride
c) Potassium chloride
d) Mercury sulphate

View Answer

Answer: b [Reason:] Mercury chloride is known as calomel. The most important general purpose secondary electrode is calomel electrode.

3. The calomel electrodes are classified based on which of the following?
a) Materials used in the electrode
b) Amount of mercury present
c) Concentration of Kcl
d) Purity of mercury

View Answer

Answer: c [Reason:] Several convenient calomel electrodes are available. They are classified based on the concentration of Kcl.

4. Which of the following calomel electrodes are used for accurate work?
a) Saturated calomel electrode
b) Electrode with 0.1M Kcl
c) Electrode with 1M Kcl
d) Electrode with 2M Kcl

View Answer

Answer: b [Reason:] Calomel electrode with 0.1M Kcl is used for accurate work. Saturated calomel electrodes are easy to prepare and maintain.

5. Calomel electrode can behave as which of the following components?
a) Anode only
b) Cathode only
c) Anode or cathode
d) Salt bridge

View Answer

Answer: c [Reason:] Calomel electrode can behave as anode or cathode depending upon the half cell. A salt bridge is used for coupling.

6. When the calomel electrode acts as the cathode which of the following does not occur?
a) Mercury ions are discharged at the electrode
b) More calomel passes into the solution
c) There is a decrease in the concentration of chloride ions
d) There is an increase in the concentration of chloride ions

View Answer

Answer: d [Reason:] When the calomel electrode acts as the cathode. When the calomel electrode acts as the cathode, mercury ions are discharged at the electrode. More calomel passes into the solution. Hence, there is an increase in the concentration of chloride ions.

7. Which of the following is not the characteristics of calomel electrode?
a) The potential of electrode is not temperature dependent
b) Preparation of electrode is easy
c) Value of potential or emf is higher for lower concentration of Kcl
d) Value of potential decreases with increasing concentration of Kcl

View Answer

Answer: a [Reason:] The potential of calomel electrode is temperature dependent. When temperature changes potential comes to a new value. It cannot be used in places where high temperatures exist.

8. Which of the following is not the characteristics of silver/silver chloride electrode?
a) These electrodes have good electrical and chemical stability
b) It can be used in temperatures greater than 600oC
c) It can be used in places or solutions that have strong reducing agents
d) It should not be used in solutions that contain proteins, sulphide or bromide

View Answer

Answer: c [Reason:] The silver/silver chloride electrode cannot be used in places or solutions that have strong reducing agents. They will reduce the silver ions to silver metal.

9. While using reference electrodes, the internal liquid level should always be kept above that of the sample solution.
a) True
b) False

View Answer

Answer: a [Reason:] While using reference electrodes, the internal liquid level should always be kept above that of the sample solution. This is done to prevent contamination of the electrolyte solution.

10. Which of the following salt bridge solutions must be used for silver/silver chloride electrode?
a) Saturated KCl
b) Saturated K2SO4
c) Saturated LiCl
d) Saturated KNO3

View Answer

Answer: a [Reason:] Saturated KCl is used as the salt bridge solution for silver/silver chloride electrode. It can also be used for calomel electrode.

11. LiCl salt bridge is more suitable in organic solvents than KCl.
a) True
b) False

View Answer

Answer: a [Reason:] LiCl salt bridge is more suitable in organic solvents than KCl. It is used for the measurement of non-aqueous solutions.

Set 4

1. Sensitivity is the ratio of peak signal amplitude to which of the following?
a) Time
b) Rms noise
c) Average noise
d) Peak-to-peak noise

View Answer

Answer: Sensitivity is the ratio of peak signal amplitude to rms noise. It is a measure of ability of an instrument to differentiate signal from surrounding noise.

2. Which of the following is not an operating technique for sensitivity enhancement?
a) Optimization of sample volume
b) Optimization of instrumental parameters
c) Optimization of noise
d) Time averaging

View Answer

Answer: c [Reason:] There are only three operating techniques for sensitivity enhancement. Optimization of noise is not an operating technique for sensitivity enhancement.

3. Which of the following techniques do not enhance sensitivity by a factor of 10 at normal operating conditions?
a) Optimization of sample volume
b) Optimization of instrumental parameters
c) Optimization of noise
d) Time averaging

View Answer

Answer: d [Reason:] Time averaging techniques does not enhance sensitivity by a factor of 10. The other two techniques enhance sensitivity by a factor of 10 at normal operating conditions.

4. The most common spherical cells have which of the following dimensions?
a) 4mm diameter
b) 40mm diameter
c) 8mm diameter
d) 80mm diameter

View Answer

Answer: a [Reason:] The most common spherical cells have 4mm diameter. A 1mm capillary cell is centred along the axis of the coil.

5. Better sensitivity with good resolution can be achieved by concentrating the sample inside which of the following?
a) Sample cell
b) Micro cell
c) Sample tube
d) Cylindrical tube

View Answer

Answer: b [Reason:] Better sensitivity with good resolution can be achieved by concentrating the sample inside a specially designed NMR microcell. It could be a spherical cell or a capillary cell.

6. Frequency spectrum of noise occupies a band that is _________ the signal spectrum. Choose the most appropriate option.
a) Narrow than
b) Wider than
c) Different from
d) Same as

View Answer

Answer: b [Reason:] Frequency spectrum of noise occupies a band that is wider than the signal spectrum. Filters operate on this concept.

7. Suppression of frequencies which contain no signal does which of the following?
a) Increases S/N ratio
b) Decreases S/N ratio
c) S/N ratio is kept constant
d) S/N ratio becomes 1

View Answer

Answer: a [Reason:] Suppression of frequencies which contain no signal increases S/N ratio. The noise decreases.

8. The amplitude of the NMR signal caused by the absorption of RF energy at the radio frequency does not depend upon the power of the RF energy applied.
a) True
b) False

View Answer

Answer: b [Reason:] The amplitude of the NMR signal caused by the absorption of RF energy at the radio frequency depends on the power of the RF energy applied. It also depends on the sweep rate selected.

9. Which of the following is not involved in signal averaging?
a) A system to repeatedly scan the spectral region of interest
b) Some storage device to store information
c) A system to coherently add individual spectra
d) Sweep generator

View Answer

Answer: d [Reason:] Sweep generator is not involved in signal averaging. This is usually accomplished using a small computer.

10. In order to have a long measuring time for increasing sensitivity, it is better to have several fast scans than a single slow scan.
a) True
b) False

View Answer

Answer: a [Reason:] In order to have a long measuring time for increasing sensitivity, it is better to have several fast scans than a single slow scan. The sensitivity increases by the square root of number of scans.

11. In Spin Decoupler, the output of the DC amplifier is applied to which of the following to control the power supplied to the oven heaters?
a) Power diode
b) Power transistor
c) Power MOSFET
d) Power IGBT

View Answer

Answer: b [Reason:] In Spin Decoupler, the output of the DC amplifier is applied to power transistor to control the power supplied to the oven heaters. The temperature is maintained at plus or minus 1oC.

12. In Spin Decoupler, the difference frequency circuit provides a means of mixing two signals and a filter to recover which of the following?
a) Low-frequency component
b) High-frequency component
c) Low-voltage component
d) High-voltage component

View Answer

Answer: a [Reason:] In Spin Decoupler, the difference frequency circuit provides a means of mixing two signals and a filter to recover low-frequency component. It is included to provide a read-out frequency.

Set 5

1. Which of the following principles are used in silica analyser?
a) Amperometric principle
b) Colorimetric principle
c) Coulometric principle
d) Magnetic principle

View Answer

Answer: b [Reason:] The principle used in silica analyser is colorimetric principle. The colour of the final solution is measured.

2. Which of the following is not added to the sample during analysis during silica analysis?
a) Ammonium Molybdate
b) Sulphuric acid
c) Reducing solution
d) Iodine solution

View Answer

Answer: d [Reason:] Iodine solution is not added to the sample during analysis. Ammonium molybdate, sulphuric acid and reducing solution are added to the sample.

3. Which of the following detectors are used in silica analyser?
a) Photovoltaic cell
b) Photo multiplier
c) Photo emissive tubes
d) Flame emission detector

View Answer

Answer: a [Reason:] Photovoltaic cell is used as detector in silica analyser. This detector does not need a battery for operation.

4. The output from both the detectors is given to which of the following devices?
a) Filters
b) Microprocessor
c) Recorder
d) Differential Amplifier

View Answer

Answer: d [Reason:] The output from both the detectors is given to the differential amplifier. The amplified signal is read through a display.

5. If the differential amplifier gives zero as output then it infers which of the following (Reference output is given to the positive terminal and sample output is given to the negative terminal)?
a) Concentration of silica in sample and reference solution is equal
b) Concentration of silica in reference solution is more than that in the sample solution
c) Concentration of silica in sample solution is more than that in the reference solution
d) Further processing is required to come to any conclusion

View Answer

Answer: a [Reason:] If the differential amplifier gives zero as output then, it means that the concentration of silica in sample and reference solution is equal. It means that the photodetectors’ output is equal.

6. If the differential amplifier gives a positive output then it infers which of the following (Reference output is given to the positive terminal and sample output is given to the negative terminal)?
a) Concentration of silica in sample and reference solution is equal
b) Concentration of silica in reference solution is more than that in the sample solution
c) Concentration of silica in sample solution is more than that in the reference solution
d) Further processing is required to come to any conclusion

View Answer

Answer: c [Reason:] If the differential amplifier gives a positive output then, it means that the concentration of silica in sample solution is more than that in the reference solution. It means that the photodetectors’ output is not equal.

7. If the differential amplifier gives a negative output then it infers which of the following (Reference output is given to the positive terminal and sample output is given to the negative terminal)?
a) Concentration of silica in sample and reference solution is equal
b) Concentration of silica in reference solution is more than that in the sample solution
c) Concentration of silica in sample solution is more than that in the reference solution
d) Further processing is required to come to any conclusion

View Answer

Answer: b [Reason:] If the differential amplifier gives a negative output then, it means that the concentration of silica in reference solution is more than that in the sample solution. It means that the photodetector’s output is not equal.

8. Which of the following statements are true?
a) More light is absorbed if the silica content is high in a solution
b) More light is transmitted if the silica content is high in a solution
c) Less light is absorbed if the silica content is high in a solution
d) More light is absorbed if the silica content is low in a solution

View Answer

Answer: a [Reason:] More amount of light is absorbed if the silica content is high in a solution. Less amount of light is transmitted if the silica content is high in a solution.

9. How will the photodetector output be if silica content is high in a solution?
a) Output will be high
b) Output will be low
c) Output will be zero
d) Output cannot be determined

View Answer

Answer: b [Reason:] If silica content is high in a solution, the detector output will be low. This is because more light is absorbed by the solution and less amount of light is transmitted.

10. What will be the final colour of the solution obtained during silica analysis?
a) Pink
b) Red
c) Blue
d) Yellow

View Answer

Answer: c [Reason:] This method works on the principle of molybdenum blue method. Hence, the colour of the final solution will be blue.

11. During the first sequence of the process, sample is added at the last.
a) True
b) False

View Answer

Answer: a [Reason:] During the first sequence of the process, sample is added at the last. During the second sequence, all the solutions are added in normal manner.

12. Blank use compensates for the effect of temperature variation.
a) True
b) False

View Answer

Answer: a [Reason:] Blank use compensates for the effect of temperature variation. It also compensates for various other variables such as ageing of lamps and coloration of the sample.