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Multiple choice question for engineering

Set 1

1. Optical fiber sensors are electrically _____
a) active
b) passive
c) active as well as passive
d) cannot be determined

View Answer

Answer: b [Reason:] Optical fiber sensors are electrically passive and consequently immune to electromagnetic disturbances. They are geometrically flexible and corrosion resistant. They can be miniaturized and are most suitable for telemetry applications.

2. Optical fibers are not immune to ________
a) electronic disturbances
b) magnetic disturbances
c) ambient light interference
d) electromagnetic disturbances

View Answer

Answer: c [Reason:] Optical fibre sensors are non-electrical and hence are free from electrical interference usually associated with electronically based sensors. Ambient light can interfere. Consequently the sensor has to be applied in a dark environment or must be optically isolated.

3. Optical fiber sensors are not immune to electromagnetic disturbances.
a) True
b) False

View Answer

Answer: b [Reason:] Optical fiber sensors are electrically passive and consequently immune to electromagnetic disturbances. They are geometrically flexible and corrosion resistant. They can be miniaturized and are most suitable for telemetry applications.

4. In which of the following optic fiber sensor the fiber is simply used to carry light to and from an external optical device where the sensing takes place?
a) extrinsic fiber optic sensor
b) energized fiber optic sensor
c) all fibers are used to simply carry light to and from the external optical devices
d) intrinsic fiber optic sensor

View Answer

Answer: a [Reason:] In an extrinsic fiber optic sensor fiber is simply used to carry light to and from an external optical device where the sensing takes place. In intrinsic fiber optic sensor one or more of the physical properties of the fiber undergo a change.

5. On the bases of application of optic fiber sensor, which of the following is not considered to be the classification of fiber optic sensor?
a) biomedical/photometric sensors
b) physical sensors
c) thermal sensors
d) chemical sensors

View Answer

Answer: c [Reason:] The variations in the returning light are sensed using a photodetector. Such sensors monitor variations either in the amplitude or frequency of the reflected light. Two of the most important physical parameters that can be advantageously measured using fibre optics are temperature and pressure.

6. Linear encoders gives ___________ output.
a) angular
b) analog
c) digital
d) unstable

View Answer

Answer: b [Reason:] Linear encoders give output in digital form. These transducers are basically encoded disks or rulers with digital pattern photographically etched on glass plate. These patterns are decoded using a light source and an array of photodetectors.

7. The type of sensor that detects the analyte species directly through their characteristic spectral properties is called
a) chemical sensor
b) thermal sensor
c) light sensor
d) Spectroscopic Sensors

View Answer

Answer: d [Reason:] Spectroscopic Sensors is the one that detects the analyte species directly through their characteristic spectral properties. In these sensors, the optical fibre functions only as a light guide, conveying light from the source to the sampling area and from the sample to the detector. Here, the light interacts with the species being sensed.

8. How many coils are required to make LVDT
a) 4
b) 6
c) 3
d) 2

View Answer

Answer: c [Reason:] Total 3 coils are required in LVDT. One centered coil which is the energizing or primary coil connected to the sine wave oscillator. The other two coils are the secondary coils so connected that their outputs are equal in magnitude but opposite in phase.

9. A chemical transduction system is interfaced to the optical fibre at its end. This type of sensor is called ?
a) chemical sensor
b) thermal sensor
c) photoelectric sensor
d) light sensor

View Answer

Answer: a [Reason:] In the chemical sensors, a chemical transduction system is interfaced to the optical fibre at its end. In operation, interaction with analyte leads to a change in optical properties of the reagent phase, which is probed and detected through the fibre optic. The optical property measured can be absorbance, reflectance or luminescence.

10. Which of the following is a displacement transducer?
a) thermistor
b) lvdt
c) strain gauge
d) thermocouple

View Answer

Answer: b [Reason:] LVDT is a displacement transducer. Thermocouple and thermistor are temperature transducers. Strain gauge is a pressure transducer.

Set 2

1. Source of Bioelectric potential is ____________ in nature.
a) electronic
b) electric
c) ionic
d) mechanical

View Answer

Answer: c [Reason:] Bioelectric potentials are generated at cellular level and the source of these potentials is ionic in nature. The prominent ions are K+, Na+, and Cl. Electronic potential is seen in commonly used cells for example the Galvanic cell. Mechanical potential is found nowhere. Electrical potential is found in electricity.

2. Palsied muscles mean _____________
a) paralyzed muscles
b) active muscles
c) voluntary muscles
d) involuntary muscles

View Answer

Answer: a [Reason:] Palsied is an adjective that means paralyzed. It is used to describe a muscle on which an individual has lost all control (cannot move). Voluntary muscles are the muscles on which the individual has complete control. Involuntary muscles are the ones on which the individual has no control for example heart wall muscles.

3. The principal ion that is not involved with the phenomena of producing cell potentials is ______________
a) sodium
b) potassium
c) chlorine
d) hydrogen

View Answer

Answer: d [Reason:] Sodium (Na+), Potassium (K+), and Chlorine (Cl) are the principal ions involved with the phenomena of producing cell potentials. Na+ is present outside the cell membrane and creates a positively charged environment outside the cell membrane. Cl- is present inside the cell membrane and is responsible for the negative environment inside the cell membrane.

4. What is the relatively static membrane potential of quiescent cells called?
a) half-cell potential
b) action potential
c) resting membrane potential
d) cell potential

View Answer

Answer: c [Reason:] Resting membrane potential or the resting potential is the relative static membrane potential of quiescent cell. That is if resting membrane potential of a neuron is about -70 mV (mV=millivolt) it means that the inside of the neuron is 70 mV less than the outside of the neuron. An action potential occurs when the potential of the membrane of a given axonal position increases and decreases rapidly. This depolarization causes depolarization of adjacent positions in a similar way.

5. The variation of the electrical potential associated with the passage of a pulse along the membrane of a muscle cell or a nerve cell is called __________
a) muscle potential
b) action potential
c) resting potential
d) half cell potential

View Answer

Answer: b [Reason:] An action potential occurs when the potential of the membrane of a given axonal position increases and decreases rapidly. This depolarization causes depolarization of adjacent positions in a similar way. Resting membrane potential or the resting potential is the relative static membrane potential of quiescent cell.

6. Cells depolarize and action potential in generated as soon as a stimulus is applied.
a) True
b) False

View Answer

Answer: b [Reason:] This statement is False. This is because unless a stimulus above a certain minimum value is applied, the cell will not be depolarized and no action potential will be generated. This value of potential above which the depolarizes and an action potential is generated is known as the stimulus threshold.

7. After a cell is stimulated, a finite period of time is required for the cell to return to its pre-stimulus state. This period is known as ____________
a) restoration period
b) refactory period
c) regain period
d) regenerative period

View Answer

Answer: b [Reason:] After a cell is stimulated, a finite period of time is required for the cell to return to its pre-stimulus state. This is because the energy associated with the action potential is developed from metabolic process within the cell which takes time for completion. This time period is called refactory period.

8. Electrooculography (EOG/E.O.G.) is a technique for measuring what?
a) abnormal function of the retina
b) heart rate
c) respiration rate
d) cornea-retinal standing potential

View Answer

Answer: d [Reason:] Electrooculography (EOG / E.O.G) is a technique for measuring the potential of the corneal retinal standing potential that exists between the front and back of the human eye. The resulting signal is called electrooculogram. The main applications are in the diagnosis of ophthalmology and the recording of eye movements.

9. EKG stands for _________________
a) Electrocardiography
b) Electroencephalography
c) Electromyography
d) Electrtokinetcography

View Answer

Answer: a [Reason:] Electrocardiography (ECG or EKG) is the way toward recording the electrical action of the heart over some stretch of time utilizing anodes put on the skin. It could simply be understood as the electrical representation of heart beat. Electroencephalography is the electrical recording of brain.

10. Phonocardiography is listening to __________
a) arm muscle sound
b) lungs sound
c) heart sound
d) respiratory tract sound

View Answer

Answer: c [Reason:] A phonocardiogram (or PCG) is a record high-constancy recording of sounds and mumble made by the heart with the assistance of the machine called phonocardiography. Consequently, phonocardiography is the chronicle of the considerable number of sounds made by the heart amid a heart cycle. Mostly stethoscope is used phonocardiography.

Set 3

1. The minimum input of physical parameter that will create a detectable out change is called __________
a) threshold
b) sensitivity
c) span
d) precision

View Answer

Answer: b [Reason:] The sensitivity of the sensor is defined as the slope of the output characteristic curve. In simple words The minimum input of physical parameter that will create a detectable out change is called sensitivity. Total operating range of the transducer is called its span.

2. The total operating range of the transducer is called __________
a) span
b) threshold
c) offset
d) drift

View Answer

Answer: a [Reason:] The total operating range of the transducer is called span of the transducer. Offset is the output that will exist when it should be zero. Drift is basically the change in a signal over long period of time.

3. Hysteresis is no change in output with the same value of input.
a) True
b) False

View Answer

Answer: b [Reason:] Hysteresis is change in output with the same value of input but with a different history of input variation. Hysteresis is observed when the input/output characteristics for a transducer are different for increasing inputs than for decreasing outputs. It results when some of the energy applied for increasing inputs is not recovered when the input decreases.

4. The region in which the output does not changes with increase in input is called _________
a) input range
b) threshold
c) offset
d) saturation

View Answer

Answer: d [Reason:] The region in which the output does not changes with increase in input is called saturation. The threshold of the transducer is the smallest change in measurant that will result in a measurable change in the transducer output. Offset is the output that will exist when it should be zero.

5. Ability of the sensor to repeat a measurement when put back in the same environment is called ______
a) conformance
b) saturation
c) repeatability
d) threshold

View Answer

Answer: c [Reason:] Ability of the sensor to repeat a measurement when put back in the same environment is called repeatability. The region in which the output does not changes with increase in input is called saturation. The threshold of the transducer is the smallest change in measurant that will result in a measurable change in the transducer output.

6. Closeness of a calibration curve to a specified curve for an inherently non linear transducer is called ___________
a) conformance
b) linearity
c) saturation
d) hysteresis

View Answer

Answer: a [Reason:] Conformance indicates the closeness of a calibration curve to a specified curve for an inherently non linear transducer. Hysteresis is change in output with the same value of input but with a different history of input variation. The region in which the output does not changes with increase in input is called saturation.

7. The range between the maximum and minimum values is applied to a parameter which can be measured is ___________
a) repeatability
b) span
c) input range
d) output range

View Answer

Answer: b [Reason:] Input range is the range between the max and min values is applied parameter which can be measured . Ability of the sensor to repeat a measurement when put back in the same environment is called repeatability. The total operating range of the transducer is called span of the transducer.

8. Which of the following is not a static property?
a) repeatability
b) hysteresis
c) frequency response
d) saturation

View Answer

Answer: c [Reason:] Frequency response is the change of transfer function with frequency, both in magnitude and in phase. It is a dynamic property. Ability of the sensor to repeat a measurement when put back in the same environment is called repeatability. The region in which the output does not changes with increase in input is called saturation.

9. Time for the sensor to reach a stable output once it is turned on is called _________
a) frequency response
b) span
c) response time
d) settling time

View Answer

Answer: d [Reason:] Settling time is the time for the sensor to reach a stable output once it is turned on. Frequency response is the change of transfer function with frequency, both in magnitude and in phase. The total operating range of the transducer is called span of the transducer.

10. Which of the following is not a dynamic property?
a) frequency response
b) saturation
c) settling time
d) response time

View Answer

Answer: b [Reason:] The region in which the output does not changes with increase in input is called saturation. It is a static property of the transducer. Settling time is the time for the sensor to reach a stable output once it is turned on. Frequency response is the change of transfer function with frequency, both in magnitude and in phase.

Set 4

1. What is the principle behind photoelectric transducers?
a) conversion of wind energy to electrical energy
b) conversion of light energy to electrical energy
c) conversion of mechanical energy to electrical energy
d) conversion of electrical energy to light energy

View Answer

Answer: b [Reason:] Photoelectric transducers are based on the principle of conversion of light energy into electrical energy. This is done by causing the radiation to fall on a photosensitive element and measuring the electrical current so generated with a sensitive galvanometer directly or after suitable amplification.

2. Which of the following material is used to build photovoltaic cells ?
a) selenium
b) celenuim
c) silicon
d) iron

View Answer

Answer: a [Reason:] Photovoltaic or barrier layer cells usually consist of a semiconducting substance, which is generally selenium deposited on a metal base which may be iron and which acts as one of the electrodes. The semiconducting substance is covered with a thin layer of silver or gold deposited by cathodic deposition in vacuum. This layer acts as a collecting electrode.

3. Selenium cells are sensitive to almost the entire range of wavelengths of the spectrum.
a) True
b) False

View Answer

Answer: a [Reason:] Selenium cells are sensitive to almost the entire range of wavelengths of the spectrum. However, their sensitivity is greater within the visible spectrum and highest in the zones near to the yellow wavelengths.

4. Which of the following is not a photoemissive cell?
a) high vacuum photocells
b) barrier layer cell
c) gas-filled photocell
d) photomultiplier tubes

View Answer

Answer: c [Reason:] Barrier layer cells are photovoltaic cells. They consist of a semiconducting substance, which is generally selenium deposited on a metal base which may be iron and which acts as one of the electrodes. Photovoltaic cells are very robust in construction, need no external electrical supply and produce a photocurrent sometimes stronger than other photosensitive elements.

5. Photo-diodes work in ____
a) forward biased
b) reverse biased
c) independent of forward and reverse biasing
d) any configuration

View Answer

Answer: b [Reason:] The photodiode is a P-N junction semiconductor diode. It always operated in the reversed biased condition. The light is always focused through a glass lens on the junction of the photo diode.

6. Photovoltaic cells need external electrical supply to function?
a) True
b) False

View Answer

Answer: b [Reason:] Photovoltaic cells are very robust in construction, need no external electrical supply and produce a photocurrent sometimes stronger than other photosensitive elements. Typical photocurrents produced by these cells are as high as 120 mA/lumen. At constant temperature, the current set up in the cell usually shows a linear relationship with the incident light intensity.

7. The instruments which give direct reading of the temperature at the thermistor position are known as _________
a) thermistor
b) telethermometers
c) rtd
d) tempothermometer

View Answer

Answer: b [Reason:] The instruments which give direct reading of the temperature at the thermistor position are known by the name telethermometers. This is because of their ability to use leads which are hundreds of feet long without a significant decrease in accuracy. The continuous signal is also suitable for recording without amplification.

8. Which of the following is a photoemissive cell ?
a) photomultiplier tubes
b) barrier layer cell
c) galvanic cell
d) rochell-salt cell

View Answer

Answer: a [Reason:] Photomultiplier tubes are photoemissive cells. These type to cells do require an external power supply to provide a sufficient potential difference between the electrodes to facilitate the flow of electrons generated at the photosensitive cathode surface. Also, amplifier circuits are invariably employed for the amplification of this current.

9. Cesium-silver oxide cells are sensitive to the near infrared wavelengths.
a) True
b) False

View Answer

Answer: a [Reason:] Cesium-silver oxide cells are sensitive to the near infrared wavelengths. Potassiumsilver oxide and cesium-antimony cells have maximum sensitivity in the visible and ultraviolet regions. The spectral response also depends partly on the transparency to different wavelengths of the medium to be traversed by the light before reaching the cathode.

10. Thermister is used to measure ____________
a) temperature
b) pressure
c) height
d) displacement

View Answer

Answer: a [Reason:] Thermistor is used to measure temperature. It is a temperature transducer. With change in temperature its resistance changes. Thus its working principle is variable resistance. Thermistors are the oxides of certain metals like manganese, cobalt and nickel which have large negative temperature coefficient, i.e. resistance decreases with increase in temperature.

Set 5

1. Which amplifier will reject any common mode signal that appears simultaneously at both amplifier input terminal and amplifies only the voltage difference that appears across its input terminals?
a) ac coupled amplifiers
b) differential amplifiers
c) carrier amplifiers
d) dc amplifiers

View Answer

Answer: b [Reason:] Differential amplifier is one which will reject any common mode signal that appears simultaneously at both amplifier input terminals and amplifies only the voltage difference that appears across its input terminals. Most of the amplifiers used for measuring bioelectric signals are of the differential type. AC amplifiers have a limited frequency response and are, therefore, used only for special medical applications such as electrocardiograph machine.

2. Which amplifier has a limited frequency response?
a) differential amplifier
b) dc amplifiers
c) ac coupled amplifiers
d) carrier amplifiers

View Answer

Answer: b [Reason:] AC amplifiers have a limited frequency response and are, therefore, used only for special medical applications such as electrocardiograph machine. For electrocardiograms, an ac amplifier with a sensitivity, giving 0.5 mV/cm, and frequency response up to 1 kHz and an input impedance of 2 to 5 MW is used. For such applications as retinography, EEG and EMG, more sensitive ac amplifiers are required, giving a chart sensitivity of say 50 mV/cm with a high input impedance of over 10 MW.

3. ______________ are used with transducers which require an external source of excitation.
a) carrier amplifiers
b) dc amplifiers
c) ac coupled amplifiers
d) differential amplifier

View Answer

Answer: a [Reason:] Carrier amplifiers are used with transducers which require an external source of excitation. They are characterized by high gain, negligible drift, extremely low noise and the ability to operate with resistive, inductive or capacitive type transducers. They essentially contain a carrier oscillator, a bridge balance and calibration circuit, a high gain ac amplifier, a phase-sensitive detector and a dc output amplifier.

4. DC amplifiers are employed with _______ feedback type.
a) positive
b) negative
c) depends on the application
d) can be any positive or negative does’t matter

View Answer

Answer: b [Reason:] DC amplifiers are generally of the negative feedback type. They are used for medium gain applications down to about 1 mV signal levels for full scale. They are not practical for very low level applications because of dc drift and poor common-mode rejection capabilities.

5. DC amplifiers are mostly used for very low level applications because they offer very less dc drift and high common mode rejection capabilities.
a) True
b) False

View Answer

Answer: b [Reason:] DC amplifiers are not practical for very low level applications because of dc drift and poor common-mode rejection capabilities. They are usually employed as pen drive amplifiers in direct writing recorders. They are used for medium gain applications down to about 1 mV signal levels for full scale.

6. Chopper stabilized dc amplifiers are complex amplifiers having ________ amplifiers incorporated in the module.
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: c [Reason:] Chopper stabilized dc amplifiers are used for low level but preferably wideband applications such as oscilloscopes, tape recorders and light beam oscilloscope recorders. These are complex amplifiers having three amplifiers incorporated in the module. This includes an ac amplifier for signals above about 20 Hz, a dc chopper input amplifier for signals from about 20 Hz down to dc plus a wideband feedback stabilized dc amplifier.

7. Which of the following amplifier is employed with resistive transducers which require an external source of excitation?
a) differential amplifier
b) ac coupled amplifier
c) carrier amplifier
d) dc bridge amplifier

View Answer

Answer: d [Reason:] DC bridge amplifiersare employed with resistive transducers which require an external source of excitation. Essentially, the amplifier comprises of a stable dc excitation source, a bridge balance and calibration unit, a high gain differential dc amplifier and a dc output amplifier. They can be used as conventional dc high gain amplifiers and offer operating simplicity and high frequency response.

8. When two wires of different material are joined together at either ends, forming two junctions which are maintained at different temperature, a _________ force is generated
a) thermo-motive
b) electro-motive
c) chemical reactive
d) mechanical

View Answer

Answer: a [Reason:] When two wires of different material are joined together at either ends, forming two junctions which are maintained at different temperature, a thermo-motive force is generated causing a current to flow around the circuit. This arrangement is called thermocouple. The junction at higher temperature in thermocouple is termed as measuring junction. The junction at lower temperature in the thermocouple is called the reference temperature.

9. Chopper input dc amplifiersare preferred for low level inputs to instrumentation systems because of their high sensitivity, negligible drift and excellent common mode rejection capability.
a) True
b) False

View Answer

Answer: a [Reason:] True. Chopper input dc amplifiersare preferred for low level inputs to instrumentation systems because of their high sensitivity, negligible drift and excellent common mode rejection capability. Their high frequency response is limited to about one half of the input chopper frequency.

10. The junction at higher temperature in thermocouple is termed as measuring junction.
a) True
b) False

View Answer

Answer: a [Reason:] The junction at higher temperature in thermocouple is termed as measuring junction.the junction at lower temperature in the thermocouple is called the reference temperature. The cold junction is usually kept at 0*C.