Multiple choice question for engineering
1. Optical radiations involve _________
a) optoelectric devices
b) biological devices
c) mechanical devices
d) chemical devices
Answer: a [Reason:] Emission and absorption of optical radiations are carried out by making use of optoelectric devices.
2. Photoelectric transducers consist of _______
a) 1 transducer
b) 3 transducers
c) 5 transducers
d) 10 transducers
Answer: b [Reason:] A photoelectric transducer consists of 3 transducers. They are as follows:
3. Photoconductive transducers produce output
a) due to change in inductance
b) due to change in light
c) due to change in resistance
d) due to change in temperature
Answer: c [Reason:] A photoconductive transducer produces an output due to a change in the resistance. Electrical output is produced due to a variation in the temperature.
4. Commonly used photoemissive material is _______
Answer: d [Reason:] Cesium-antimony is the most commonly used photoemissive material. The photoemissive material is housed in a glass tube. Photoemissive devices are also called as phototubes.
5. Phototubes are very quick in response to light.
Answer: a [Reason:] Phototubes are quick in response to light. Phototubes are used in applications which require light pulses of very short durations to be observed.
6. Photoconductors are made of _______
a) thick layer of semiconductor
b) thin layer of semiconductor
c) capacitive substrate
d) inductive substrate
Answer: b [Reason:] Photoconductors comprise of a thin layer of semiconductor. Photoconductors not consisting of a junction are known as junction less detectors.
7. When an open circuited pn junction is illuminated
a) resistance increases
b) there is no effect
c) electron hole pairs are formed
d) capacitance increases
Answer: c [Reason:] Upon illumination of an open circuited pn junction, electron hole pairs are generated. A small voltage appears across the junction and as a result it acts as a voltae source.
8. Optocoupler consists of a phototransistor and a led.
Answer: a [Reason:] The optocoupler consists of a phototransistor and an infrared emitting diode. Wavelength of the emitting and receiving diodes must be matched in order to get a proper output.
9. Response time for gas-filled phototubes is _______
Answer: d [Reason:] Gas filled phototubes are generally very slow in response as compared to vacuum phototubes. This is due to the slow movement of ions towards the photocathode.
10. Reverse leakage current in a transistor _______
a) is affected by light
b) is not affected by light
c) increases with decrease in pressure
d) decreases with increase in temperature
Answer: a [Reason:] The reverse leakage current in a transistor is directly proportional to the intensity of light. It increases with the increase in the light intensity.
1. Piezoelectric transducer is used for measuring
a) non-electrical quantities
b) electrical quantities
c) chemical quantities
d) any quantity
Answer: a [Reason:] A piezoelectric transducer is used for measuring non-electrical quantities such as vibration, acceleration, pressure and the intensity of sound.
2. Piezoelectric crystals __________
a) float on water
b) dissolve in water
c) are not soluble in water
d) absorb water
Answer: b [Reason:] A piezoelectric crystal dissolves in water. It is fully soluble in water. When the temperature is humid, the piezoelectric crystals gets dissolved in water.
3. Piezoelectric crystals produce _________
a) no voltage
b) low voltage
c) high voltage
d) very high voltage
Answer: c [Reason:] Piezoelectric crystals can be used spark ignition engines. They are also used in electrostatic dust filters and produce high voltage at low current.
4. Piezoelectric transducer consists of _________
a) copper rod
b) aluminum wire
c) gold crystal
d) quartz crystal
Answer: d [Reason:] A piezoelectric transducer consists of a quartz crystal. It comprises of silicon and oxygen arranged in a crystal structure of SiO2.
5. When a compressive force is applied to a quartz crystal
a) positive charges are induced
b) negative charges are induced
c) no charge is induced
d) both positive and negative charges are induced
Answer: a [Reason:] When a quartz crystal is subjected to a compressive stress, positive charges are induced in one side of the crystal while negative charges are induced on the other side of the crystal.
6. In kitchen applications a piezoelectric crystal is used for _________
a) skimming milk
b) lighting a gas stove
Answer: b [Reason:] A piezoelectric lighter is used for lighting a gas based stove in kitchen applications. The pressure induced on the piezoelectric sensor creates an electric signal leading to a spark.
7. A piezoelectric transducer has a _________
a) very high sensitivity
b) low sensitivity
c) high sensitivity
d) zero sensitivity
Answer: c [Reason:] The sensitivity is high in a piezoelectric transducer. A piezoelectric transducer can be used as a sensor. It can also be used in an accelerometer due to its good frequency response.
8. A piezoelectric transducer is used as an ignition source for a cigarette.
Answer: a [Reason:] Cigarettes use piezoelectric transducers as a source of ignition. They are also used in the measurement of sonar, microphone, pressure, displacement and force.
9. Microphone converts light into heat.
Answer: b [Reason:] A microphone is used to convert the pressure induced in the form of sound waves into electric signal. The electrical signal is then amplified to produce louder sound.
10. A quartz crystal is _________
a) a chemical transducer
b) a photoelectric transducer
c) not a self-generating transducer
d) a self-generating transducer
Answer: d [Reason:] The quartz crystal is a self-generating transducer. It does not need any electric voltage for operation. The quartz crystal becomes short in length due to an applied electric field in the opposite direction.
1. In a potentiometric DVM ________
a) voltage is compared
b) current is compared
c) resistance is compared
d) power is compared
Answer: a [Reason:] Potentiometric integrating type DVM employs voltage comparison. The unknown voltage is compared with a reference. The reference value is set by a calibrated potentiometer.
2. How to obtain balance?
a) by using a detector
b) by changing the pot setting
c) by supplying voltage
d) by using a transformer
Answer: b [Reason:] Balance is obtained in a potentiometric integrating type DVM by adjusting the settings of the potentiometer. The dial setting of the potentiometer gives the value of the unknown voltage.
3. In a potentiometric DVM, balance is obtained manually.
Answer: b [Reason:] Balance is obtained in a potentiometric integrating type DVM by adjusting the settings of the potentiometer. Hence in a potentiometric integrating type DVM, the balance is obtained automatically.
4. Unknown voltage is __________
a) converted to current
d) measured using a voltmeter
Answer: c [Reason:] In a potentiometric integrated type DVM, the unknown voltage is filtered. It is also attenuated to a suitable magnitude. This forms the input for the comparator. A chopper is usually used as the error detector.
5. How is the reference voltage obtained?
a) from a fixed current source
b) from a variable voltage source
c) from a variable current source
d) from a fixed voltage source
Answer: d [Reason:] Reference voltage is applied to the potentiometer. It is obtained from a source of fixed voltage. Position of the slider on the contact surface determines the value of the feedback voltage.
6. Feedback voltage is applied to the ________
b) error amplifier
d) sliding contact
Answer: a [Reason:] Comparator accepts the feedback voltage as an input. Comparator compares the values of the unknown voltage and the feedback voltage. Comparator then provides the difference between the feedback voltage and the unknown voltage as its output.
7. Output of the comparator is known as ________
a) amplified signal
b) error signal
c) feedback signal
d) attenuated signal
Answer: b [Reason:] Comparator then provides the difference between the feedback voltage and the unknown voltage as its output. This is also known as the error signal.
8. Slider movement depends on ________
a) current magnitude
b) resistance magnitude
c) voltage magnitude
d) power magnitude
Answer: c [Reason:] In a potentiometric integrating type DVM, the slider moves based on the magnitude of the feedback voltage with respect to the input voltage. Contact is pushed back to the place where the unknown voltage equals the feedback voltage.
9. Accuracy of a potentiometric DVM is ________
Answer: d [Reason:] In a potentiometric integrating type DVM, the accuracy is usually high. It generally depends on the reference of the digital to analog converter. Accuracy of the voltage to frequency converter is less important compared to that of the digital to analog converter.
1. Potentiometric resistance transducer measures __________
a) linear displacement
b) rectangular displacement
c) square displacement
d) triangular displacement
Answer: a [Reason:] A Potentiometric resistance transducer measures linear displacement. It can also be used for measuring angular displacement.
2. Resistance potentiometer consists of _________
a) capacitive element
b) resistive element
c) inductive element
d) no elements
Answer: b [Reason:] A resistance potentiometer consists of a resistive element. It also has a sliding contact known as a wiper.
3. Resistance transducer has _________
a) medium efficiency
b) low efficiency
c) high efficiency
d) zero efficiency
Answer: c [Reason:] A resistance transducer has a high electrical efficiency. It provides sufficient amount of output for further control operations.
4. What is a helipot?
a) inductive element
d) resistive element
Answer: d [Reason:] A resistive transducer in the form of a helix is also known as a heliport. They are used for measuring linear as well as angular motion.
5. Resistance potentiometers convert mechanical displacement into _________
a) electrical signal
b) chemical signal
c) physical output
d) kinetic energy
Answer: a [Reason:] Resistive transducers are used for transforming the mechanical displacement into electrical signal. Linear displacement is applied to the sliding contact which then converts the change in resistance into voltage or current.
6. Strain gauge is a _________
a) inductive transducer
b) resistive transducer
c) capacitive transducer
d) mechanical transducer
Answer: b [Reason:] A strain gauge is a resistive transducer. It works on the principle of mechanical displacement into a change in resistance.
7. Strain is defined as _________
a) change in height per unit height
b) change in weight per unit weight
c) change in length per unit length
d) change in diameter per unit diameter
Answer: c [Reason:] Strain is defined as the ratio of two quantities as follows:
Strain = ∆l⁄l where,
l is the length
∆l is the change in length.
8. Stress is defined as _________
a) diameter per unit area
b) length per unit area
c) weight per unit area
d) force per unit area
Answer: d [Reason:] Stress is defined as the ratio of two quantities as follows:
Stress = Force⁄Area The unit of stress is N / m2.
9. Stress vs strain curve is always linear.
Answer: b [Reason:] Within the elastic limits, the curve of stress vs strain is linear. Strain measurements must be made on the free surface of any body. A strain gauge is usually used to measure the magnitude of strain.
10. Sensitivity is the smallest value of measurable strain.
Answer: a [Reason:] The smallest value of strain that can be measured is known as the sensitivity of the body. Type of strain gauge used dictates the maximum value of strain that can be measured.
1. Pressure is the _________
a) force per unit area
b) mass per unit area
c) force per unit volume
d) mass per unit volume
Answer: a [Reason:] Pressure at a point is defined as the force acting per unit area. It is measured at some given point over a surface.
2. Pressure measurement devices make use of ________
a) non-elastic member
b) elastic member
c) bendable member
d) non-bendable member
Answer: b [Reason:] Pressure sensors employ elastic member at the input stage to detect or sense the pressure variations. Elastic members are usually of various forms and convert the pressure into mechanical displacement.
3. Output of electrical transducer is ________
a) inversely proportional to displacement
b) proportional to square of displacement
c) proportional to displacement
Answer: c [Reason:] The output of an electrical transducer is proportional to displacement. Displacement is measured using electrical transducers.
4. In general how many pressure sensitive devices are there?
Answer: d [Reason:] Usually there are four pressure sensitive devices. They are as follows:
• Bourdon tube
5. Diaphragms in a pressure sensor are of ________
a) 2 types
b) 5 types
c) 10 types
d) 20 types
Answer: a [Reason:] Generally in a pressure sensor we have four pressure sensitive devices. Diaphragm is a type of a pressure sensitive device. They are of two types:
• Flat type
• Corrugated type.
6. Temperature is the only consideration while selecting a diaphragm.
Answer: b [Reason:] While selecting a suitable diaphragm for sensing the pressure the following factors are considered important.
• Temperature range
• Shock and vibration
• Frequency response requirements.
7. Capsule type of pressure sensor consists of ________
a) 6 dissimilar diaphragms
b) 4 identical diaphragms
c) 2 identical diaphragms
d) 8 dissimilar diaphragms
Answer: c [Reason:] Capsule is a type of a pressure sensor. It comprises of two identical annular corrugated metal diaphragms that are sealed together to form a shell like enclosure.
8. Bourdon tubes are ________
a) very highly sensitive to shock
b) not sensitive to shock
c) less sensitive to shock
d) more sensitive to shock
Answer: d [Reason:] Bourdon tube is one type of pressure sensor. It is more sensitive to shock and vibrations as compared to diaphragms. Bourdon tube can be used for precision measurements of pressure up to 3 MN / m2.
9. Bellows have 5 to 20 convolutions.
Answer: a [Reason:] Bellow is a type of pressure sensor. They have about 5 to 20 convolutions. The number of convolutions depends on the pressure range, displacement, and operating temperature.
10. Sensitivity in a capsule is increased ________
a) through parallel connection of capsules
b) through series connection of capsules
c) through series and parallel connection of capsules
d) by not connecting them at all
Answer: b [Reason:] Capsule is a type of a pressure sensor. In a capsule we can increase the sensitivity by connecting two or more capsules in series. The resultant displacement is equal to the number of capsules.