Multiple choice question for engineering
Set 1
1. Which of the following produces the electron beam in magnetic deflection mass spectrometer?
a) Tungsten filament
b) Quartz rod
c) Silica
d) Rhodium filament
Answer
Answer: a [Reason:] Tungsten filament produces the electron beam in magnetic deflection mass spectrometer. The electrons are produced by the heated filament.
2. In magnetic deflection mass spectrometer, in which of the following ways is acceleration applied to the direction of motion?
a) In random manner
b) Parallel to it
c) Perpendicular to it
d) Along it
Answer
Answer: c [Reason:] Acceleration in mass spectrometer, is applied perpendicular to the direction of motion. The velocity of the object remains constant.
3. Direct focussing is obtained by deflecting the ion beam along a _________ trajectory through the magnetic field.
a) 120o
b) 150o
c) 190o
d) 180o
Answer
Answer: d [Reason:] Direct focussing is obtained by deflecting the ion beam along a 180o trajectory through a magnetic field. The gap between the poles must be large enough to contain the ion source.
4. Which of the following separate the ions according to their mass-to-charge?
a) Ion source
b) Detector
c) Magnetic sector
d) Electric sector
Answer
Answer: c [Reason:] Magnetic sector will separate the ions according to their mass-to-charge. The magnet will decide the mass to charge ratio.
5. Mattauch-Herzog geometry involves a deflection of which of the following radians in a radial electrostatic field analyser?
a) √2Π
b) Π/2
c) Π/3√4
d) Π/4√2
Answer
Answer: d [Reason:] Mattauch-Herzog geometry involves a deflection of Π/4√2 radians in a radial electrostatic field analyser. It is followed by a magnetic deflection of Π/2 radians.
6. Which of the following leads to limitation of resolution?
a) All ions do not have same energy
b) All ions do not have same charge
c) All ions are not of the same size
d) All ions do not have the same charge
Answer
Answer: a [Reason:] The resolution is limited as all ions do not have the same energy. Hence, the ions would not have the same velocity.
7. The electric sector field is not subject to hysteresis.
a) True
b) False
Answer
Answer: a [Reason:] The electric sector field is not subject to hysteresis. Hence, the relationship between mass to charge ratio and accelerating voltage is linear.
8. Which of the following components need to be added in order to increase the resolution?
a) Ion source
b) Detector
c) Magnetic sector
d) Electric sector
Answer
Answer: d [Reason:] Electric sector needs to be added in order to increase the resolution. This compensates for the decrease in resolution due to varying velocities.
9. Which of the following is commonly varied in magnetic deflection mass spectrometer?
a) Electric sector
b) Magnetic fold strength
c) Magnetic constant
d) Electric constant
Answer
Answer: b [Reason:] Magnetic fold strength is usually varied in magnetic deflection mass spectrometer. Electric sector is kept constant.
10. Nier-Johnson geometry involves a deflection of which of the following radians in a radial
electrostatic field analyser?
a) Π
b) Π/2
c) Π/3
d) Π/4
Answer
Answer: b [Reason:] Nier-Johnson geometry involves a deflection of Π/2 radians in a radial electrostatic field analyser. A magnetic deflection of Π/3 radians follows the analyser.
11. An accuracy of 1 part in 102 has been obtained in precision mass measurements.
a) True
b) False
Answer
Answer: b [Reason:] An accuracy of 1 part in 109 has been obtained in precision mass measurements. Spectrographs with photographic reading are used for analysis of solids.
Set 2
1. Which of the following is the formula for pH calculation?
a) log10[H+].
b) -log10[H+].
c) log2[H+].
d) -log2[H+].
Answer
Answer: b [Reason:] pH is defined as the negative logarithm of hydrogen ion concentration. Hence, its formula is -log10[H+].
2. Pure water is known to be which of the following?
a) Weak electrolyte
b) Strong electrolyte
c) Neither weak nor strong
d) Not an electrolyte
Answer
Answer: a [Reason:] Pure water is a weak electrolyte. It dissociates to form hydrogen ions and hydroxyl ions.
3. Which of the following is the value of hydrogen ion concentration of pure water?
a) 1×107 moles/litre
b) 1×105 moles/litre
c) 1×106 moles/litre
d) 1×108 moles/litre
Answer
Answer: a [Reason:] The hydrogen ion concentration of pure water is 1×107 moles/litre. It can be represented as [H+]=1×107 moles/litre.
4. Which of the following is the value of hydroxyl ion concentration of pure water?
a) 1×107 moles/litre
b) 1×105 moles/litre
c) 1×106 moles/litre
d) 1×108 moles/litre
Answer
Answer: a [Reason:] The hydroxyl ion concentration of pure water is 1×107 moles/litre. It can be represented as [OH-]=1×107 moles/litre.
5. Which of the following is the relation between hydrogen and hydroxyl ion concentration of pure water?
a) Value of hydrogen ion concentration is greater
b) Value of hydroxyl ion concentration is greater
c) They are both always the same
d) The concentrations keep changing
Answer
Answer: c [Reason:] In water, the value of hydrogen and hydroxyl ion concentrations are the same. It can be represented as [H+]=[OH-].
6. The Nernst equation is given by which of the following statements?
a) E=Eo + 2.303 RT/F log CH
b) E=Eo – 2.303 RT/F log CH
c) E=Eo + 2.303 RT×F log CH
d) E=Eo – 2.303 RT×F log CH
Answer
Answer: a [Reason:] The Nernst equation is represented as, E=Eo + 2.303 RT/F log CH. it is used for measuring the potential of electrodes.
7. Which of the following is the relation between concentration of hydrogen and hydroxyl ions in an acidic solution?
a) Value of hydrogen ion concentration is greater
b) Value of hydroxyl ion concentration is greater
c) They are both always the same
d) The concentrations keep changing
Answer
Answer: a [Reason:] In acidic solution, the value of hydrogen ion concentration is greater than that of hydroxyl ion concentration. It can be represented as [H+]>[OH-].
8. Which of the following is the relation between concentration of hydrogen and hydroxyl ions in a basic solution?
a) Value of hydrogen ion concentration is greater
b) Value of hydroxyl ion concentration is greater
c) They are both always the same
d) The concentrations keep changing
Answer
Answer: b [Reason:] In basic solution, the value of hydroxyl ion concentration is greater than that of hydrogen ion concentration. It can be represented as [H+]<[OH-].
9. The measurement of hydrogen ion concentration can be made by measuring the potential developed in an electrochemical cell.
a) True
b) False
Answer
Answer: a [Reason:] The measurement of hydrogen ion concentration can be made by measuring the potential developed in an electrochemical cell.
10. Slope factor is independent of temperature.
a) True
b) False
Answer
Answer: b [Reason:] Slope factor is dependent on temperature. Slope factor is given by – 2.303 RT/F.
Set 3
1. pH meters can be considered as voltage sources with which of the following internal resistances?
a) Very low resistance
b) Moderate resistance
c) Very high resistance
d) No resistance
Answer
Answer: c [Reason:] pH meters can be considered as voltage sources with very high internal resistance. In order to eliminate errors no current should flow from the source.
2. The electrodes used in pH measurement have which of the following internal resistances?
a) Very low resistance
b) Moderate resistance
c) Very high resistance
d) No resistance
Answer
Answer: c [Reason:] The electrodes used in pH measurement have very high internal resistance. It is of the order of 1000M ohm.
3. Which of the following is not a failure in pH meters?
a) Defective electrodes
b) Defective input circuitry
c) Defective electronic circuitry
d) Defective calibration
Answer
Answer: d [Reason:] Defective calibration is not a failure in pH meters. Failure occurs due to defective electrodes, defective input circuitry and defective electronic circuitry.
4. Which of the following is the simplest of pH meters?
a) Null-detector type pH meter
b) Direct reading type pH meter
c) Digital pH meter
d) Modern pH meter
Answer
Answer: a [Reason:] Null-detector type pH meter is the simplest of all pH meters. It is also known as the potentiometer type.
5. In which of the following ways can zero drift be reduced in pH meters?
a) Using filter
b) Giving zero adjustment arrangement
c) Keeping the input impedance high
d) Using balanced and differential amplifiers
Answer
Answer: d [Reason:] Zero drift be reduced in pH meters using balanced and differential amplifiers. Their response to external signals are additive and to internal noise are subtractive.
6. Which of the following can be used to provide automatic temperature compensation?
a) Proper insulation
b) Calibration for different temperatures
c) Thermistor
d) Thermometer
Answer
Answer: c [Reason:] To provide automatic temperature compensation, thermistors must be used. As temperature of the solution changes, the circuit constants are altered accordingly.
7. Which of the following is not the characteristic of null-detector type pH meter?
a) It can be battery operated
b) It has less accuracy
c) It is easy to maintain
d) Its electronic circuits are simple
Answer
Answer: b [Reason:] Null-detector type pH meter has greater accuracy than 0.01 pH. pH value is read from the calibrated precision voltage source dial.
8. Which of the following is not the characteristic of direct reading type pH meters?
a) Simple operation
b) Quick to use
c) Continuous indication output
d) It requires balancing process
Answer
Answer: d [Reason:] Direct reading type pH meters do not require balancing process. Its operation is simple and readings can be read directly.
9. Which of the following is not the characteristic of chopper amplifier pH meter?
a) Direct voltage from the electrodes is chopped at the main frequency
b) Using choppers for high-input resistance gives rise to spikes of waveforms at the output
c) It leads to stability in DC output of phase-sensitive rectifier
d) Magnitude of surge increases in the glass electrode output
Answer
Answer: c [Reason:] The use of chopper amplifier in pH meter leads to zero instability. It leads to various other problems for high-input resistance.
10. In which of the following ways can the disadvantages of chopper amplifier type pH meter be
overcome?
a) Using zero corrected DC amplifier
b) Using modern design
c) Using digital design
d) Using vibrating condenser
Answer
Answer: d [Reason:] The disadvantages of chopper amplifier type pH meter can be overcome using a vibrating condenser. It is used in the place of the mechanical chopper.
11. The zero stability of vibrating condenser amplifier type pH meter is much better than direct coupled amplifier.
a) True
b) False
Answer
Answer: a [Reason:] The zero stability of vibrating condenser amplifier type pH meter is much better than direct coupled amplifier. The capacity can be changed by vibrating one of its plates.
12. In vibrating condenser amplifier type pH meter, to maintain good performance which of the following has to be done?
a) Frequency of the vibrator should be stable
b) Frequency of the vibrator should be constant
c) Amplitude of the vibrator should be constant
d) Both frequency and amplitude of the vibrator should be constant and stable
Answer
Answer: d [Reason:] In vibrating condenser amplifier type pH meter, to maintain good performance, both frequency and amplitude of the vibrator should be constant and stable.
13. If an instrument fails to balance at zero, it is most likely that the electrodes are defective.
a) True
b) False
Answer
Answer: b [Reason:] If an instrument fails to balance at zero, it is most likely that the electronic circuitry is defective. Errors may also occur due to leakage of capacitance.
14. Given below is the block diagram of digital pH meter. Identify the unmarked component.
a) Filter
b) Buffer
c) A/D converter
d) D/A converter
Answer
Answer: c [Reason:] The unmarked component is A/D converter. Microprocessor operates only on digital data. Electrodes give analog signals. Hence, A/D converter must be present.
Set 4
1. A discriminator circuit is which of the following circuits?
a) Wheatstone bridge
b) Instrumentation amplifier
c) Astable multivibrator
d) Schmitt trigger
Answer
Answer: d [Reason:] A discriminator circuit is a Schmitt trigger circuit. There are two discriminator circuits in pulse height analyser.
2. Which of the following is the function of the discriminator?
a) Rejects signals below a certain voltage
b) Rejects signals above a certain voltage
c) Rejects signal in a range alone
d) Filters noise alone
Answer
Answer: a [Reason:] The discriminator can be set to reject signals below a certain voltage. This is required for excluding scattered radiation and noise.
3. The difference between the pulses having amplitudes between the two triggering levels is called as __________
a) Pulse width
b) Energy gap
c) Window width
d) Amplitude variation
Answer
Answer: c [Reason:] The difference between the pulses having amplitudes between the two triggering levels is called as window width. It is also called the channel width.
4. The pulses having amplitudes between the two triggering levels are given by which of the following components?
a) Pre-amplifiers
b) Linear amplifiers
c) Anti-coincidence circuits
d) Discriminators
Answer
Answer: d [Reason:] The pulses having amplitudes between the two triggering levels are given by discriminators. There are two discriminators.
5. Schmitt triggers are followed by which of the following components?
a) Pre-amplifier
b) Linear amplifier
c) Anti-coincidence circuit
d) Discriminator
Answer
Answer: c [Reason:] Schmitt triggers are followed by anti-coincidence circuits. The output of anti-coincidence circuit is given to counters.
6. Which of the following components cancels all the pulses which trigger both the discriminators?
a) Pre-amplifier
b) Linear amplifier
c) Anti-coincidence circuit
d) Discriminator
Answer
Answer: c [Reason:] Anti-coincidence circuit cancels all the pulses which trigger both the discriminators. The output of anti-coincidence circuit is given to counters.
7. Which of the following is used when the number of channels is ten or less?
a) Two discriminators in series
b) Two discriminators in parallel
c) Series array of discriminators
d) Parallel array of discriminators
Answer
Answer: d [Reason:] Parallel array of discriminators are used when the number of channels is ten or less. If the number is more than ten this is not preferred.
8. If number of channels is more than ten, the problems of stability of discrimination voltages arise.
a) True
b) False
Answer
Answer: a [Reason:] If number of channels is more than ten, the problems of stability of discrimination voltages arise. Problems also arise with increase of adequate differential non-linearity.
9. The signal reaching which of the following components is the one lying in the window of pulse height analyser?
a) Pre-amplifier
b) Linear amplifier
c) Counter
d) Discriminator
Answer
Answer: c [Reason:] The signal reaching the counter is the one lying in the window of pulse height analyser. Scalar and counter follow the anti-coincidence circuit.
10. The measurement of pulse height is useful for energy determination.
a) True
b) False
Answer
Answer: a [Reason:] The measurement of pulse height is useful for energy determination. This is accomplished by the pulse height analyser.
Set 5
1. Which of the following is not a feature of quadrupole mass spectrometer?
a) Low cost
b) Light weight
c) Low speed electronic scanning
d) Simple in construction
Answer
Answer: c [Reason:] In quadrupole mass spectrometer, electronic scanning takes place. The scanning takes place in high speed.
2. Which of the following is not a component of quadrupole mass filter?
a) Electrodes
b) Choke
c) DC potential
d) Detector
Answer
Answer: d [Reason:] Detector is not a part of the filter. The filter uses DC potential.
3. The mass selection scheme uses a dc potential and not a radio frequency potential.
a) True
b) False
Answer
Answer: b [Reason:] The mass selection scheme uses a dc potential. It also uses a radio frequency potential.
4. If to one pair of electrodes one potential with one sign is applied, which of the following is applied to the other pair of electrodes?
a) Same potential with same sign
b) Different potential with same sign
c) Different potential with different sign
d) Same potential with different sign
Answer
Answer: d [Reason:] If to one pair of electrodes one potential with one sign is applied, same potential with different sign is applied to the opposite electrodes.
5. Which of the following is the heart of quadrupole instrument?
a) Electrodes
b) Choke
c) DC potential
d) Detector
Answer
Answer: a [Reason:] Electrodes are the heart of quadrupole instrument. Opposite electrodes are electrically connected.
6. Which of the following has to be done to increase the resolution of the quadrupole mass spectrometer?
a) Increasing distance between detector and reflectron
b) Increasing difference between the individual rf accelerating stages
c) Increasing the length of the drift tube
d) Increasing the rod length of the electrode
Answer
Answer: d [Reason:] The resolution depends upon the electrode. The length of the electrode has to be increased for increasing the resolution.
7. Which of the following does not affect resolution of the instrument?
a) Changing length of electrode
b) Changing slope of scan line
c) Quality of machining of the rods
d) Changing length of drift tube
Answer
Answer: d
Explantion: Changing length of drift tube does not affect resolution of the instrument. Increase in resolution results in an increase in the number of ions reaching the detector.
8. In cases where a differentiation is required between very similar substances, which of the following techniques making use of quadrupole principle is preferred?
a) Evaporation mass spectrometry
b) Pyrolysis mass spectrometry
c) Plasma mass spectrometry
d) Trapped ion mass spectrometry
Answer
Answer: b [Reason:] In cases where a differentiation is required between very similar substances, pyrolysis mass spectrometry is used. The sample is usually solid or involatile liquid in thiscase.
9. In pyrolysis spectrometry heating is done until which of the following is reached?
a) Curie point
b) Boiling point
c) Until production of superheated vapour
d) Until 100oC
Answer
Answer: a [Reason:] In pyrolysis spectrometry heating is done until curie point is reached. At this point magnetic permeability drops abruptly.
10. Which of the following is used to cool the ion source?
a) Liquid sodium shield
b) Liquid nitrogen shield
c) Water
d) Freon
Answer
Answer: b [Reason:] Liquid nitrogen cooled shield is used to cool the ion source. It reduces source contamination.
11. In quadrupole mass spectrometer, the ratio u/v is mass dependent, where ‘u’ is the DC voltage and ‘v’ is the peak amplitude.
a) True
b) False
Answer
Answer: b [Reason:] In quadrupole mass spectrometer, the ratio u/v is mass independent, where ‘u’ is the DC voltage and ‘v’ is the peak amplitude. This ratio is kept constant.
12. When value of q is kept constant, the value of m/e is proportional to which of the following when ‘m’ is the mass number, ‘e’ is the electric charge, ‘u’ is the DC potential, ‘v’ is the peak amplitude and ‘f’ is the frequency?
a) u/v ratio
b) u
c) v
d) f
Answer
Answer: When value of q is kept constant, the value of m/e is proportional to ‘v’. By
variation of rf amplitude the m/e ratio varies.