Competitive Electrical Measurements MCQs – Transducers ( Electrical Measurements ) MCQs
Latest Electrical Measurements MCQs
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Electrical Measurements MCQs – Transducers ( Electrical Measurements ) MCQs
The most occurred mcqs of Transducers ( ) in past papers. Past papers of Transducers ( Electrical Measurements ) Mcqs. Past papers of Transducers ( Electrical Measurements ) Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related Transducers ( Electrical Measurements ) Mcqs. The Important series of Transducers ( Electrical Measurements ) Mcqs are given below:
Strain Gauge Measurement Technique
1. Strain gauge measurement involves __________
a) Wheatstone bridge
b) Kelvin bridge
c) De Sauty’s bridge
d) Anderson bridge
Answer: a
Explanation: Strain gauge makes use of the practical form of Wheatstone’s bridge to measure the strain developed by an element.
2. Load cell is used for the measurement of _______
a) area
b) force
c) mass
d) length
Answer: b
Explanation: The load cell is used in a semiconductor strain gauge for the measurement of force. Load cells measure the deformation that is produced by force or weight.
3. Strain is a _______
a) fractional change in volume
b) fractional change in area
c) fractional change in length
d) fractional change in height
Answer: c
Explanation: Strain is defined as the fractional change in length of a body. A change in resistance of the element is reflected in the form of strain of the gauge as well as the element.
4. Semiconductor strain gauge uses _______
a) rectifier circuitry
b) power electronics circuitry
c) ordinary bridge circuit
d) bridge circuit with temperature compensation
Answer: d
Explanation: The semiconductor strain gauge makes use of a Wheatstone practical bridge circuit along with temperature compensation. Output is made linear as the resistance characteristics with respect to strain are non-linear.
5. A semiconductor strain gauge consists of how many dummy gauges?
a) 2
b) 4
c) 6
d) 10
Answer: a
Explanation: The semiconductor strain gauge consists of two dummy gauges in the form of two arms of the Wheatstone bridge circuit. Dummy gauges are used for temperature compensation.
6. Metals in strain gauge construction have _______
a) non-linear temperature coefficient
b) linear temperature coefficient
c) tangential temperature coefficient
d) exponential temperature coefficient
Answer: b
Explanation: The metals used in a strain gauge construction have a linear temperature coefficient. A change in the temperature affects the resistance and varies the value of strain.
7. A Wheatstone bridge has _______
a) low sensitivity
b) zero sensitivity
c) high sensitivity
d) infinite sensitivity
Answer: c
Explanation: A Wheatstone bridge circuit has a high sensitivity for detecting very small variation in the values of resistance. We can connect the strain gauge in one of the arms of a Wheatstone bridge and measure the strain in terms of variation in resistance.
8. Load cells are calibrated such that _______
a) force varies inversely with resistance
b) force varies as the square of resistance
c) force remains constant with resistance
d) force varies directly with resistance
Answer: d
Explanation: The load cells in a semiconductor strain gauge are calibrated in such a way that the force or weight varies directly as the resistance. The strain gauge is arranged in the form of a bridge.
9. Load cell is sensitive to minute strains.
a) True
b) False
Answer: a
Explanation: A load cell responds to very minute variation in the value of strain. It is sensitive to high values of the load.
10. Mass of only about 20 kg can be measured by a load cell.
a) True
b) False
Answer: b
Explanation: Using a load cell a mass or weight of the order of 20 kg to 20,000 kg can be measured. By making use of appropriate load cells we can measure forces as high as 5 MN.
Resistance Temperature Detector
1. Resistance temperature detector is ___________
a) a electrical transducer
b) a mechanical transducer
c) a chemical transducer
d) a physical transducer
Answer: a
Explanation: Resistance temperature detector is an electrical transducer. It is used for measuring the variation in temperature. It is also known as a resistance thermometer.
2. Relation between temperature and resistance of a conductor is ________
a) Rt = Rref [1+t]
b) Rt = Rref [1+α∆t]
c) Rt = Rref [1-αt]
d) Rt = Rref [1-t]
Answer: b
Explanation: The relationship between temperature and resistance of a conductor is given by
Rt = Rref [1+α∆t]
where, Rt is the resistance of the conductor at t°C.
Rref is the resistance of the conductor at reference temperature
α is the temperature coefficient of resistance
∆t is the difference between the temperature being measured and the reference temperature.
3. Sensing element in the thermometer must provide ________
a) small change in resistance
b) no change in resistance
c) large change in resistance
d) infinite change in resistance
Answer: c
Explanation: The sensing element in a thermometer must give a large change in the resistance for a given change in the temperature.
4. Platinum is used for industrial applications because ________
a) it is cheap
b) it is available readily
c) it is a noble metal
d) it gives accurate measurements
Answer: d
Explanation: In industrial applications, platinum is used due to its accuracy in providing measurements. It is also reproducible. Platinum element can be used for the measurement of temperatures of about 1000 K.
5. Resistance thermometer provides the change in electrical resistance.
a) True
b) False
Answer: a
Explanation: A resistance thermometer provides a change in the electrical resistance with respect to a variation in the temperature. Basically resistance thermometers work on the principle of change in the electrical resistance with variation in the temperature.
6. If the sensing element is large, then less amount of heat is required.
a) True
b) False
Answer: b
Explanation: When the sensing element in a resistance thermometer is small in size, then less quantity of heat is required to raise the temperature. Platinum, nickel and copper are the commonly used metals for measuring temperature.
7. Most metallic conductors have a ________
a) neutral temperature coefficient of resistance
b) negative temperature coefficient of resistance
c) positive temperature coefficient of resistance
d) zero temperature coefficient of resistance
Answer: c
Explanation: In general metallic conductors have a positive temperature coefficient of resistance. The resistance increases with an increase in temperature.
8. In a temperature sensing element ________
a) low value of α is required
b) infinite value of α is required
c) α must be zero
d) high value of α is required
Answer: d
Explanation: In order to achieve a large change in the value of resistance for a small change in the value of temperature, high value of α is required. Change in resistance is measured through a Wheatstone’s bridge.
9. Nickel and its alloys can be used over a temperature range of ________
a) 100 to 450 K
b) 10 to 50 K
c) 0 to 25 K
d) 5 to 15 K
Answer: a
Explanation: Temperature sensors constructed using nickel and its alloys can be used in the temperature range of 100 to 450 K. Compared to platinum, they are less expensive. They have a comparatively higher temperature coefficient that increases with temperature.
10. How can corrosion be prevented in a resistance thermometer?
a) by immersing the setup in oil
b) by enclosing the elements in a glass tube
c) by using guard rings
d) by painting the elements
Answer: b
Explanation: Corrosion can be eliminated in a resistance thermometer by enclosing the elements in a protective tubular glass made of pyrex, quartz or crystal depending upon the temperature range.
Thermistor
1. Thermistor is a contraction _________
a) thermal resistor
b) laser resistor
c) electric resistor
d) mechanical resistor
Answer: a
Explanation: Thermistor is basically the short form of a thermal resistor. Resistors which depend on temperature are known as thermal resistors.
2. Thermistors have ________
a) positive temperature coefficient
b) negative temperature coefficient
c) zero temperature coefficient
d) infinite temperature coefficient
Answer: b
Explanation: Thermistor generally has a negative temperature coefficient of resistance. With an increase in temperature, resistance of a thermistor decreases.
3. Thermistors ________
a) sense large changes in temperature
b) cannot sense any change in temperature
c) sense small changes in temperature
d) have a positive temperature coefficient of resistance
Answer: c
Explanation: Thermistors can sense very small changes in temperature. The negative temperature coefficient of thermistors can be a few percent/degree celcius change in temperature.
4. Thermistor has a resistance of ________
a) 250 ῼ to 500 kῼ
b) 50 ῼ to 10 kῼ
c) 1 ῼ to 1 kῼ
d) 100 ῼ to 100 kῼ
Answer: d
Explanation: Thermistor has a resistance range of 100 ῼ to 100 kῼ. Thermistor consists of a mixture of metallic oxides of manganese, nickel, cobalt, copper, iron and uranium.
5. Thermistors are suited for precision temperature measurements.
a) True
b) False
Answer: a
Explanation: Thermistors can be used for precision measurement of temperature, controlling g temperature and for temperature compensation due to a very large variation in resistance with temperature.
6. Change in resistance is measured using a ________
a) Anderson’s bridge
b) Wheatstone’s bridge
c) Hay’s bridge
d) Maxwell’s bridge
Answer: b
Explanation: The change in resistance in a thermistor is measured using a Wheatstone’s bridge. It is used for measurement of resistance in the range of -100°C to +200°C.
7. Thermistor material is pressed ________
a) under zero pressure
b) under low pressure
c) under high pressure
d) under low volume
Answer: c
Explanation: A thermistor material is usually pressed under high pressure to form a flat cylindrical shape. Disks and washers are placed in series or in parallel to increase the power dissipation.
8. Thermistor follows which law for small variations ________
a) Charle’s law
b) KVL
c) KCL
d) Ohm’s law
Answer: d
Explanation: For small changes in the values of current, voltage across a thermistor increases. It attains a peak value. Then the voltage across the thermistor decreases. As a result Ohm’s law is followed at small variations of current.
9. At small values of voltage, a thermistor ________
a) reaches peak current slowly
b) reaches peak current immediately
c) does not reaches peak current
d) reaches peak current intermediately
Answer: a
Explanation: For minute variations in voltage, thermistor reaches peak value of current slowly. As the magnitude of voltage is increased, less time is required to attain peak current.
10. Thermistor has low resistance.
a) True
b) False
Answer: b
Explanation: Thermistor generally has a very high value of resistance. Cables with shield are required to be used for minimising interference.
Pressure Sensor
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
Explanation: 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
Explanation: 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
d) constant
Answer: c
Explanation: 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?
a) 6
b) 20
c) 10
d) 4
Answer: d
Explanation: Usually there are four pressure sensitive devices. They are as follows:
• Diaphragms
• Capsule
• Bourdon tube
• Bellows.
5. Diaphragms in a pressure sensor are of ________
a) 2 types
b) 5 types
c) 10 types
d) 20 types
Answer: a
Explanation: 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.
a) True
b) False
Answer: b
Explanation: 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
Explanation: 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
Explanation: 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.
a) True
b) False
Answer: a
Explanation: 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
Explanation: Capsule is a type of 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.
Inductive Transducer
1. Mutual inductance between two coils is given as _________
a) M = kL1L2−−−−√
b) M = kL1−−√
c) M = kL2−−√
d) M = L1L2−−−−√
Answer: a
Explanation: The mutual inductance between two coils is given by the relation
M = kL1L2−−−−√
where, k is the coefficient of coupling
M is the mutual inductance between the coils.
2. Mutual inductance depends on _________
a) self-inductance
b) self-inductance and coefficient of coupling
c) coefficient of coupling
d) permittivity of air
Answer: b
Explanation: The mutual inductance of a pair of coils depends on the self-inductance of the individual coils and on the coefficient of coupling.
3. Self-inductance of an inductor is given by ________
a) L = N⁄S
b) L = 1⁄S
c) L = N2⁄S
d) L = N2
Answer: c
Explanation: The self-inductance of an inductor is obtained by making use of the relation
L = N2⁄S
where, N is the number of coil
S is the reluctance of the coil (A/Wb).
4. Reluctance of a coil is given by which of the following relation?
a) S = 1⁄A
b) S = 1⁄μ
c) S = a⁄μA
d) S = 1⁄μA
Answer: d
Explanation: The reluctance of an inductance coil is given by the relation
S = 1⁄μA
where, l is the length of the magnetic circuit (m)
a is the area of the magnetic circuit which encloses the flux (m2)
µ is the permeability of the core (H/m).
5. Self-inductance depends on ________
a) permeability
b) permittivity
c) plank’s constant
d) rydberg constant
Answer: a
Explanation: The self-inductance of an inductor is obtained by making use of the relation
L = N2⁄S
where, N is the number of coil
S is the reluctance of the coil (A/Wb)
As reluctance depends on the permeability, the self-inductance of a coil depends on the permeability.
6. What is the relation between the self-inductance and the reluctance of a coil?
a) directly proportional
b) inversely proportional
c) no relation
d) constant
Answer: b
Explanation: The self-inductance of an inductor is obtained by making use of the relation
L = N2⁄S
where, N is the number of coil
S is the reluctance of the coil (A/Wb)
We observe from the above equation that the self-inductance of a coil is inversely proportional to its reluctance.
7. Based on self-inductance of a coil, how many types of inductive transducers are available?
a) 5
b) 10
c) 4
d) 20
Answer: c
Explanation: Based on the self-inductance of an inductive coil, there are four types of inductive transducers available. They are as follows:
i) Variable permeability inductive transducer
ii) Variable reluctance inductive transducer
iii) Eddy current inductive transducer
iv) Linear variable differential transducer.
8. In an eddy current transducer output depends on the variation in the eddy current.
a) True
b) False
Answer: a
Explanation: An eddy current transducer is a self-generating type of inductive transducer. In an eddy current transducer, output depends on the change in the value of the eddy current at the input.
9. An inductive transducer measures the variation in ________
a) reluctance
b) resistance
c) capacitance
d) self-inductance
Answer: d
Explanation: Inductive transducer measures the variation in the self-inductance and mutual inductance of an inductive coil. Variation in the inductance is measured as a change in the displacement.
10. Inductive transducer is used for the measurement of physical quantities.
a) True
b) False
Answer: a
Explanation: An inductive transducer is usually used for the measurement of physical quantities such as pressure, force, displacement, position, vibration, velocity, etc.
Capacitive Transducer
1. Capacitance of a parallel plate capacitor is ________
a) C = A∈⁄d
b) C = ∈⁄d
c) C = A⁄d
d) C = A
Answer: a
Explanation: The capacitance of a parallel plate capacitor is given by the relation,
C = A∈⁄d
where,
A is the area of cross section of the plates
d is the distance of separation between the plates
∈ is the permittivity of space.
2. A capacitive transducer works on the principle of ________
a) inductance
b) capacitance
c) resistance
d) reluctance
Answer: b
Explanation: A capacitive transducer works on the principle of capacitance. The capacitance of a system depends on the dielectric used as well as the properties of a capacitive system.
3. Capacitance of a cylindrical capacitor is given by which of the following relation?
a) C = \frac{∈l}{ln(\frac{R}{r})}
b) C = \frac{2πl}{ln(\frac{R}{r})}
c) C = \frac{2π∈l}{ln(\frac{R}{r})}
d) C = \frac{2π∈}{ln(\frac{R}{r})}
Answer: c
Explanation: The capacitance of a cylindrical capacitor is given by the relation
C = 2π∈lln(Rr)
where, l is the length of the cylinder
R is the inner radius of the external cylinder
r is the outer radius of the inner cylinder.
4. Capacitance can be varied in ________
a) 10 ways
b) 6 ways
c) 2 ways
d) 4 ways
Answer: d
Explanation: Capacitance is varied in four ways. They are as follows:
Change of distance
Change in dielectric
Change in common plate area
Using quartz diaphragms.
5. Capacitive pressure transducer uses distance of separation for sensing the capacitance.
a) True
b) False
Answer: a
Explanation: A capacitive pressure transducer is based on the principle of distance of separation between the plates of the capacitor. Capacitance of a parallel plate capacitor varies when the distance between the two parallel plates changes.
6. Capacitive transducer displays ________
a) linear behaviour
b) non-linear behaviour
c) exponential behaviour
d) tangential behaviour
Answer: b
Explanation: A capacitive transducer displays non-linear behaviour. This is due to stray electric fields. Guard rings are required to eliminate the edge effects and the parasitic electric field effects.
7. Frequency response of capacitive transducers is ________
a) high
b) medium
c) low
d) zero
Answer: c
Explanation: In a capacitive transducer, long leads and cables are used. Due to loading effect, frequency response is poor and the sensitivity reduces.
8. What is the relation between capacitance and output impedance?
a) proportional to square
b) constant
c) directly proportional
d) inversely proportional
Answer: d
Explanation: When the capacitance is low in the range of pico-farads, output impedance tends to a high value. This leads to loading effect.
9. What is the relation between capacitance and input impedance?
a) directly proportional
b) constant
c) proportional to square
d) inversely proportional
Answer: a
Explanation: Capacitive transducer has high input impedance. It also has a good frequency response. The loading effects are minimum.
10. Composite capacitance consists of _________
a) one dielectric medium
b) more than one dielectric medium
c) five dielectric media
d) ten dielectric media
Answer: b
Explanation: In a composite capacitance, there is more than one dielectric medium. The capacitance is given by
where, d1, d2 and d3 are the thicknesses
∈1, ∈2 and ∈3 are the permitivitties of the three different media.
Thermoelectric Transducer
1. Thermoelectric transducer is a __________
a) temperature transducer
b) pressure transducer
c) inductive transducer
d) capacitive transducer
Answer: a
Explanation: A thermoelectric transducer is a temperature transducer. It converts thermal energy into electrical energy.
2. Commonly used thermoelectric transducer is __________
a) thermometer
b) thermocouple
c) linear variable differential transducer
d) loud speaker
Answer: b
Explanation: The most commonly used thermoelectric transducer is a thermocouple. It measures the change in temperature and converts it into an electrical signal.
3. The algebraic sum of e.m.f.s in a circuit containing thermocouples is __________
a) infinite
b) hundred
c) zero
d) ten
Answer: c
Explanation: In a circuit consisting of many thermocouples, the algebraic sum of the e.m.f.s produced is zero. It remains constant with temperature.
4. What is a thermopile?
a) single thermocouple
b) series-parallel connection of thermocouples
c) parallel connection of thermocouples
d) series of thermocouples
Answer: d
Explanation: Thermopile is a series connection of thermocouples. By making use of thermopiles, a more sensitive element is obtained as compared to a single thermocouple.
5. Chromel-constantan thermopile consists of 25 thermocouples.
a) True
b) False
Answer: a
Explanation: A chromel-constantan thermopile provides a sensitivity of 1 mv/°F. It is made up of 25 thermocouples. Temperature variation as small as 0.001°F can be measured using this thermopile.
6. Thermocouple must provide ________
a) small thermo e.m.f
b) sufficient thermo e.m.f
c) no thermo e.m.f
d) infinite thermo e.m.f
Answer: b
Explanation: A thermocouple must be able to provide sufficient thermo e.m.f. This must be with respect to each degree variation in the temperature. It helps in detecting the temperature variation and in measurement.
7. Most suitable material for a thermocouple is ________
a) brass
b) gold
c) platinum
d) silver
Answer: c
Explanation: Platinum is the most suitable material for constructing thermocouples. It has a very high sensitivity. Constantan is the other material (alloy) with a composition of 40 % of Ni and 60 % of Cu used in a thermocouple.
8. If two different metals are joined forming a closed circuit an electric current flows.
a) True
b) False
Answer: b
Explanation: When two different metals are joined together forming a closed circuit, if the temperatures of the two junctions are different then an electric current flows through the circuit.
9. Which of the following should satisfy for measuring higher temperatures using a thermocouple?
a) no wire is required
b) wire must be small
c) wire must be thin
d) wire must be heavy
Answer: d
Explanation: Higher temperatures can be measured using a thermocouple by making the wire heavy. Increase in size of the wire affects the response time of the thermocouple.
10. For accurate temperature measurement in a thermocouple the __________
a) cold compensation is needed
b) hot compensation is needed
c) no compensation is needed
d) hot and cold compensations are needed
Answer: a
Explanation: Temperature can be measured accurately by using a thermocouple with cold junction temperature compensation.
Piezoelectric Transducer
1. Piezoelectric transducer is used for measuring __________
a) non-electrical quantities
b) electrical quantities
c) chemical quantities
d) any quantity
Answer: a
Explanation: 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
Explanation: 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
Explanation: 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
Explanation: 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 then ____________
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
Explanation: When a quartz crystal is subjected to 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
c) grinding
d) mixing
Answer: b
Explanation: 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
Explanation: 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.
a) True
b) False
Answer: a
Explanation: 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.
a) True
b) False
Answer: b
Explanation: 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
Explanation: 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.
Photoelectric Transducers
1. Optical radiations involve _________
a) optoelectric devices
b) biological devices
c) mechanical devices
d) chemical devices
Answer: a
Explanation: 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
Explanation: A photoelectric transducer consists of 3 transducers. They are as follows:
Photo-emissive
Photo-conductive
Photo-voltaic.
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
Explanation: 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 _______
a) gold
b) opium
c) tellurium
d) cesium-antimony
Answer: d
Explanation: 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.
a) True
b) False
Answer: a
Explanation: 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
Explanation: 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 then _________________
a) resistance increases
b) there is no effect
c) electron hole pairs are formed
d) capacitance increases
Answer: c
Explanation: 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 voltage source.
8. Optocoupler consists of a phototransistor and a led.
a) True
b) False
Answer: a
Explanation: 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 _______
a) zero
b) intermediate
c) fast
d) slow
Answer: d
Explanation: 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 a decrease in pressure
d) decreases with increase in temperature
Answer: a
Explanation: The reverse leakage current in a transistor is directly proportional to the intensity of light. It increases with the increase in light intensity.