Multiple choice question for engineering
Set 1
1. Capacitive transducers can be used by_______________
a) Measuring change in distance between plates
b) Measuring change in area of plates
c) Change in dielectric material
d) All of the mentioned
Answer
Answer: d [Reason:] Capacitance of a material is affected by area and distance of separation of plates and dielectric material.
2. Capacitive transducers cannot be used as strain gauges.
a) True
b) False
Answer
Answer: b [Reason:] Strain to be measured is applied to parallel plates of capacitor and total displacement change will be proportional to strain.
3. Which of the following is correct for capacitive transducer?
a) Capacitive strain gauges
b) Capacitive tachometers
c) Capacitive pressure transducer
d) All of the mentioned
Answer
Answer: d [Reason:] Capacitive transducers find application in measurement of both strain, pressure and angular displacement. Hence all of the mentioned can be treated as application of capacitive transducer.
4. For a material capacitance increases with _____________
a) Decrease in area of plates, all other factors constant
b) Increase in distance between plates, all other factors constant
c) Decrease in distance between plates, all other factors constant
d) None of the mentioned
Answer
Answer: c [Reason:] Capacitance can be represented as C=ε0εrA / d
Where,
εr represents dielectric constant
A is the area of plate
d is the distance between plates.
5. Which of the following is correct for moisture transducers?
a) Dielectric constant of pure water greater than other materials
b) Dielectric constant of pure water much less than other materials
c) Dielectric constant of pure water and of other materials are equal
d) None of the mentioned
Answer
Answer: a [Reason:] Dielectric constant of pure water is 80 which is much greater than other materials, this characteristic helps in measurement of moisture content.
6. Which of the following device is used for measuring relative humidity?
a) Capacitive pressure transducer
b) Hygrometer
c) Capacitive strain transducer
d) Capacitive moisture transducer
Answer
Answer: b [Reason:] Hygrometers are special devices, which are applicable for measuring relative humidity of a medium.
7. Which of the following quantities cannot be measured by capacitive transducers?
a) Displacement
b) Speed
c) Moisture
d) None of the mentioned
Answer
Answer: d [Reason:] Capacitive transducer finds application in measuring almost all quantities like displacement, thickness, moisture speed etc.
8. Which of the following have high relative permittivity?
a) Bakelite
b) Marble
c) Paraffin
d) All of the mentioned
Answer
Answer: b [Reason:] Dielectric constant or relative permittivity of Bakelite is about 4.4, for marble it vary from 8 to 10 and for paraffin it is only 2.2.
9. Capacitive microphone is an application of ______________
a) Capacitive displacement transducer
b) Capacitive moisture transducer
c) Hygrometer
d) None of the mentioned
Answer
Answer: a [Reason:] In microphone electric signals are produced according to pressure variations caused by acoustic waves, which can be easily measured by displacement transducer.
10. Thermometers are not possible using capacitive transducer.
a) True
b) False
Answer
Answer: b [Reason:] Capacitive transducers can be used to measure temperature in a way similar to moisture measurement.
Set 2
1. Find the initial value of current for which transient current is given by
I(S) = (S2+S)⁄(5S2+1)
a) 0
b) 1
c) 0.2
d) 0.5
Answer
Answer: c [Reason:] Initial value of current from transient response is found using initial value theorem on Laplace transform. Initial value theorem is given as
Ltt→0x(t)=Lts→∞S.X(S).
2. What is the purpose of making internal resistance of milli-ammeter very low?
a) High sensitivity
b) High accuracy
c) Minimum voltage drop across meter
d) Maximum voltage drop across meter
Answer
Answer: c [Reason:] Low internal resistance will help in easy current flow. If we put a high resistance in series to current flow, it will cause large voltage drop to produce across meter.
3. Which of the following devices can be used with both AC and DC?
a) PMMC
b) Moving iron type
c) Moving coil type
d) Induction type
Answer
Answer: b [Reason:] Moving iron type meters can be used in both AC and DC applications.
4. How many electrons are contributed in one coulomb electric charge?
a) 6.242 × 1018
b) 6.242 × 1019
c) 6.242 × 1020
d) 6.242 × 1010
Answer
Answer: a [Reason:] Charge of one electron is 1.6 × 10-19coulumb, hence one coulomb implies reciprocal of 1.6×10-19 which is 6.25×1018.
5. In a conductor after 1 minute of electron passage, current flown is found to be 1mA. How many electrons would have passed through that conductor?
a) 4.5×1020
b) 5×1017
c) 3.75×1017
d) 3.75×1018
Answer
Answer: c [Reason:] For n number of electrons, total charge will be n×1.6×10-19. Then for charge passed in one second will be current flow, here 1mA.
6. Which of the following can be treated as an equivalent of ampere?
a) Coulomb/second
b) Watt/second
c) Joule/second
d) Coulomb
Answer
Answer: a [Reason:] Ampere can be treated as coulomb per second, since it is the charge transferred in one second.
7. What will be the average value of current, if its peak value is 43A?
a) 27.4A
b) 37.7A
c) 21.5A
d) 60.8A
Answer
Answer: a [Reason:] Average current value is the product of peak value and 0.636.
8. Using a low resistant shunt Moving coil, permanent magnet instrument can be converted to ______________
a) Volt meter
b) Ammeter
c) Flux-meter
d) Watt meter
Answer
Answer: b [Reason:] By applying a low resistant shunt in permanent magnet moving coil instrument can be converted to Ammeter.
9. An induction meter can handle current up to__________
a) Below 10A
b) 10A
c) 50A
d) 100A
Answer
Answer: d [Reason:] Current handling capacity of induction meter is high up to 100A.
10. Which of the following effect is used in AC ammeters?
a) Electromagnetic effect
b) Electrostatic effect
c) Chemical effect
d) Magnetic effect
Answer
Answer: a [Reason:] AC ammeters uses electromagnetic principle for operation. This effect is also employed in some integrating instruments.
Set 3
1. Which of the following is correct for digital transducer?
a) Measures digital quantity only
b) Gives digital output
c) Doesn’t measure analog input
d) None of the mentioned
Answer
Answer: b [Reason:] A digital transducer is a device which gives output in digital form.
2. LDE is used for measuring ____________
a) Linear acceleration
b) Angular acceleration
c) Linear displacement
d) Linear acceleration
Answer
Answer: c [Reason:] Linear digital encode or LDE is used for measuring linear displacement.
3. Datums are used for ___________
a) Obtaining digital output
b) Converting analog data to digital data
c) Storing data
d) Displaying output
Answer
Answer: c [Reason:] Datums are used in incremental transducers which will consider previous data for display.
4. Absolute encoders require data.
a) True
b) False
Answer
Answer: b [Reason:] Absolute encoders shows the output for present input only, and it doesn’t store any previous data.
5. Which of the following is not an encoder?
a) Optical encoders
b) Magnetic encoders
c) Angular digital encoders
d) None of the mentioned
Answer
Answer: d [Reason:] Different types of encoder devices are available according to their operating medium.
6. Why positive feedback is used in pressure transducer?
a) To improve stability
b) To maintain stability constant
c) To maintain vibratory motion
d) None of the mentioned
Answer
Answer: c [Reason:] Positive feedback in vibrating diaphragm is used to maintain vibratory motion in diaphragm.
7. VDP is used for measuring pressure ____________
a) Less than 1 atmosphere
b) Between 1 and 100 atmosphere
c) Above 1000 atmosphere
d) All of the mentioned
Answer
Answer: b [Reason:] Pressure range between 1 and 100 atmosphere are measured using vibrating diaphragm pressure transducer.
8. In vibrating tube gas transducer, Pressure difference across wall is varying.
a) True
b) False
Answer
Answer: b [Reason:] Pressure difference across walls of tube in vibrating tube gas density transducer is always kept constant to measure density of liquid.
9. In vibrating string transducer output frequency is depended on length of spring by ________
a) Direct proportionality
b) Inverse proportionality
c) Equal
d) None of the mentioned
Answer
Answer: b [Reason:] Output frequency decreases as length of string is increased and they are inversely proportional.
10. Density of flowing liquid can be measured using____________
a) Vibrating tube transducer
b) Vibrating cylinder transducer
c) Both vibrating tube and cylinder transducer
d) None of the mentioned
Answer
Answer: a [Reason:] Only vibrating tube transducer allow flow of liquid and they can be used for measurement of density of flowing liquid.
Set 4
1. Electrical network made up of resistor and inductor is a ________________
a) Passive network
b) Active network
c) Low pass filter
d) High pass filter
Answer
Answer: a [Reason:] Resistor and Inductor are passive electrical components, and network made up of passive components can be termed as passive network.
2. Resistor is a ________________ element.
a) Zero order
b) First order
c) Second order
d) None of the mentioned
Answer
Answer: a [Reason:] For a zero order system transfer function will be constant and resistor can be categorize as zero order system.
R(S) =(V(S))/(I(S))
3. What is the time constant for a resistor-capacitor network?
a) R
b) C
c) R/C
d) RC
Answer
Answer: d [Reason:] For an R-C network, time constant is the product of resistance and capacitance values.
4. Cascading two first-order system doesn’t result in under-damped second order system.
a) True
b) False
Answer
Answer: a [Reason:] When two first order systems are cascaded, it produces second order critically damped or over damped system only.
5. Which of the following has transfer function G(S) =1/(1+Sτ)?
a) First order low pass filter
b) First order high pass filter
c) Notch filter
d) None of the mentioned
Answer
Answer: a [Reason:] Transfer function of a low-pass RC filter can be found as G(S) =1/(1+SRC). Where time constant τ=RC.
6. In which of the following categories RLC network can be included?
a) Zero-order system
b) First-order system
c) Second-order system
d) Third-order system
Answer
Answer: c [Reason:] Transfer function of RLC circuit is 1/(s2 LC+sRC+1) , in which highest power of ‘S’ is two and system is second-ordered system.
7. For a RC network with R=1KΩ and C=100µF .What will be the time constant of system?
a) 0.1
b) 1
c) 10
d) 0.01
Answer
Answer: a [Reason:] Time constant of a RC network is the product of resistance and capacitance values.
8. What is the Laplace transform of component inductor?
a) sL
b) L
c) L/s
d) s2L
Answer
Answer: a [Reason:] Relation between current flowing and voltage developed across an inductor is given by VL= L(dI(t))/dt and converting into Laplace domain and applying initial conditions to zero, we get
V(s) =L I(s).
9. How we can express Laplace transform of component capacitor?
a) Cs
b) C
c) 1/sC
d) 1/C
Answer
Answer: c [Reason:] Relation for a capacitor is given as1/C ∫0τi(t)dt, converting it to Laplace domain and applying zero initial conditions we get 1/sC.
10. What is the natural frequency of RLC circuit?
a) LC
b) RLC
c) √LC
d) 1/(√LC)
Answer
Answer: d [Reason:] Transfer function of RLC circuit is 1/(s2 LC+sRC+1) , while general equation of a second order system is1/(s2+2δωn s+ωn2). From the relation, ωn2=1/LC and we obtain natural frequency.
Set 5
1. Which of the following can be measured using tachometers?
a) Angular speed
b) Linear speed
c) Acceleration
d) Vibration
Answer
Answer: a [Reason:] Tachometers are special devices used to measure angular displacement of rotating shafts.
2. Two phase induction motor can be used as AC tachometers.
a) True
b) False
Answer
Answer: a [Reason:] One phase of induction motor can be used to provide reference supply and second phase can be used for providing output voltage related to speed.
3. Electrodynamic vibration transducers are based on _____________
a) Magnetostriction
b) Electromagnetic induction
c) Self inductance
d) None of the mentioned
Answer
Answer: b [Reason:] Electrodynamic vibration transducers are based on electromagnetic induction, in which magnet induces emf in a coil.
4. Which of the following is used for measuring emf between plates of transducers?
a) Low impedance voltmeter
b) High impedance voltmeter
c) Any voltmeter
d) None of the mentioned
Answer
Answer: b [Reason:] High impedance voltmeters are used for eliminating effect of drop due to internal resistance of liquid measured.
5. Which of the following is applicable for electromagnetic flow meter?
a) It causes obstruction to flow
b) It doesn’t causes obstruction t flow
c) It cannot be used in slurries
d) None of the mentioned
Answer
Answer: b [Reason:] Electromagnetic flow meters doesn’t causes obstruction to flow and can be used for measurement in slurries.
6. Which of the following quantities are sensitive to electromechanical flow meters?
a) Viscosity
b) Density
c) Temperature
d) None of the mentioned
Answer
Answer: d [Reason:] Electromagnetic flow meters are insensitive to quantities like viscosity, density, and temperature of liquid etc.
7. Which of the following represents expression of output from electromechanical flow meter?
a) BDV
b) BV
c) BD
d) BD2V
Answer
Answer: a [Reason:] Output potential of electromechanical transducer will be equal to product of magnetic flux density, diameter of pipe, and velocity of flow.
8. Electromechanical system can be used for measuring vibration.
a) True
b) False
Answer
Answer: a [Reason:] Electromechanical system can be used for measuring vibration, in which vibratory motion will be converted to output voltage.
9. Which of the following is correct for AC and DC tachometers?
a) Sensitivity if AC tachometer is very high
b) Sensitivity of DC tachometer is very high
c) Sensitivity of both are equal
d) None of the mentioned
Answer
Answer: b [Reason:] For AC tachometer it has a sensitivity which is very less than sensitivity of DC tachometers.
10. Which of the following is correct for tachometer system?
a) First order system
b) Second order system
c) Third order system
d) Unpredictable
Answer
Answer: b [Reason:] Tachometer systems are second order systems.