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Multiple choice question for engineering

Set 1

1. In an ordinary dynamometer, the deflecting torque is _________
a) small
b) medium
c) large
d) very large

View Answer

Answer: a [Reason:] The deflecting torque in an ordinary dynamometer is small. The current and pressure coils are excited. The measurement of power factor is inaccurate.

2. Errors are introduced by ________
a) capacitance
b) inductance
c) resistance
d) impedance

View Answer

Answer: b [Reason:] At low power factors in an ordinary dynamometer type wattmeter, the errors are caused due to inductance of the pressure coil.

3. Power coil has a low value of ________
a) inductance
b) capacitance
c) resistance
d) impedance

View Answer

Answer: c [Reason:] In a low power factor dynamometer type wattmeter, the pressure coil is designed in order to have a low value of resistance. The current flowing through the pressure coil is increased in order to raise the operating torque.

4. Resistance of pressure coil in a low power factor dynamometer type wattmeter is
a) once time
b) three times
c) hundred times
d) ten times

View Answer

Answer: d [Reason:] In a low power factor dynamometer type wattmeter, pressure coil has a resistance value that is one tenth of the actual with respect to unity power wattmeters. This is done in order to ensure a reasonable amount of torque at low power factors.

5. Low power factor wattmeters are designed to ________
a) have a low torque
b) have a high torque
c) have a medium torque
d) have no torque

View Answer

Answer: a [Reason:] Low power factor wattmeters have a low value of control torque. They provide full scale deflection for low values of power factors of the order of 0.1.

6. Power loss in the current coil is ________
a) less
b) more
c) intermediate
d) very less

View Answer

Answer: b [Reason:] Low power factor circuits have low power. Current coil constitutes a high current. As a result, the power loss in the current coil is high. The reading obtained from the wattmeter is prone to errors.

7. Pressure coil has no error.
a) True
b) False

View Answer

Answer: b [Reason:] Pressure coil has an error induced due to inductance. It is given by the relation EI sinΦ tanβ. As value of Φ is large for low value of power factor, the error is high in a pressure coil.

8. Error in a pressure coil can be compensated.
a) True
b) False

View Answer

Answer: a [Reason:] In a low power factor wattmeter, by connecting a capacitor of value C across a portion of the resistance R in the circuit the error in the pressure coil can be compensated.

Set 2

1. Gauge factor in a strain gauge must be ________
a) high
b) low
c) medium
d) small

View Answer

Answer: a [Reason:] The gauge factor in a strain gauge must be high. A large value of gauge factor indicates a large change in the value of resistance for a particular strain.

2. Strain gauges are used for _______
a) small scale measurements
b) dynamic measurements
c) static measurements
d) large scale measurements

View Answer

Answer: b [Reason:] Strain gauges are used for dynamic measurements. The frequency response must be better. The characteristics must be linear over the entire frequency range.

3. Resistance of the strain gauge must be _______
a) zero
b) small
c) large
d) medium

View Answer

Answer: c [Reason:] The resistance of a strain gauge must be large. Typical resistance values for a strain gauge are in the range of 120 ῼ, 350 ῼ, and 1000 ῼ.

4. Strain gauge has a _______
a) tangential
b) exponential
c) non-linear
d) linear

View Answer

Answer: d [Reason:] The strain gauge has a linear characteristic. Variation in resistance must be a linear function of the strain.

5. Strain gauge has a _______
a) low temperature coefficient of resistance
b) high temperature coefficient of resistance
c) zero temperature coefficient of resistance
d) infinite temperature coefficient of resistance

View Answer

Answer: a [Reason:] The strain gauge has a low temperature coefficient of resistance. Due to temperature variation, errors can be minimised in this way. In most of the strain gauges, temperature compensation is provided.

6. Semiconductor strain gauges are used for _______
a) low gauge factor values
b) high gauge factor values
c) zero gauge factor value
d) infinite gauge factor value

View Answer

Answer: b [Reason:] The semiconductor strain gauges are generally used when high values of gauge factors are required. The gauge factor for semiconductor gauges is 50 times higher than that for wire gauges.

7. Strain gauge works on the principle of _______
a) piezo-electric effect
b) barkhausen criterion
c) piezo- resistive effect
d) feedback element effect

View Answer

Answer: c [Reason:] A semiconductor strain gauge works on the principle of piezo-resistive effect. Piezo-resistive effect is the change in the value of the resistance due to a change in the resistivity of the semiconductor.

8. In metallic gauges resistance changes due to _______
a) temperature
b) current
c) voltage
d) dimension

View Answer

Answer: d [Reason:] The resistance varies in metallic gauges due to a change in the dimensions of the metallic gauge. Germanium and silicon are the materials used in metallic gauges.

9. Gauge factor for a semiconductor strain gauge is _______
a) 130 ± 10%
b) 30 ± 10%
c) 200 ± 10%
d) 10 ± 10%

View Answer

Answer: a [Reason:] The gauge factor for a typical semiconductor strain gauge is about 130 ± 10% for 350 ῼ. The gauge factor is measured at the room temperature. The gauge measures small strains from 0.1 to 500 microstrains.

10. Hysteresis characteristics of a semiconductor strain gauge are poor.
a) True
b) False

View Answer

Answer: b [Reason:] The hysteresis characteristics for a semiconductor strain gauge are excellent. It is less than 0.05 %.

Set 3

1. High resistances are of the order of __________
a) 0.1 Mῼ
b) 10 mῼ
c) 1 kῼ
d) 10 Gῼ

View Answer

Answer: a [Reason:] Resistances of the order of 0.1 Mῼ and above are known as high resistances. Resistance values upto 1 ῼ are known as low resistances. Resistances upto a few kῼ are known as medium resistances.

2. Megger is a ________
a) source of e.m.f
b) source to measure high resistance
c) type of a null detector
d) current carrier

View Answer

Answer: b [Reason:] Megger is a portable instrument to measure high resistances.

3. Megger is also used for ________
a) providing additional e.m.f
b) bridge balance
c) testing insulation resistance
d) controlling the temperature

View Answer

Answer: c [Reason:] A null detector is used to balance the bridge. Additional e.m.f can be provided to a circuit by increasing the magnitude of the voltage source. Megger is used for testing the insulation resistance of cables.

4. Megger works on the principle of ________
a) kirchhoff’s current laws
b) ohm’s law
c) gauss’s law
d) electromagnetic induction

View Answer

Answer: d [Reason:] Ohm’s law is applicable to only purely resistive circuits which are based on linearity principle. Megger basically works on the principle of electromagnetic induction.

5. The role of the permanent magnet in a megger is to ________
a) provide field
b) provide voltage
c) generate power
d) balance the circuit

View Answer

Answer: a [Reason:] Voltage can be provided by means of an e.m.f source. Power generation occurs when current flows through a circuit. Permanent magnet in a megger is used to provide field for the generator as well as the ohmmeter.

6. A guard ring is provided in a megger to ________
a) protect the circuit
b) eliminate error
c) reduce current flow
d) limit the temperature rise

View Answer

Answer: b [Reason:] Temperature rise can be prevented by reducing the flow of excessive current through the circuit. The role of a guard ring in a megger is to reduce the errors due to leakage current.

7. The supply to the megger is given by ________
a) ac motor
b) ac generator
c) permanent magnet dc motor
d) dc generator

View Answer

Answer: c [Reason:] Megger works on the principle of electromagnetic induction. Supply can be given through a dc motor. A permanent magnet dc motor driven by hand is used as a source of supply to the megger.

8. The moving element of the ohmmeter in a megger consists of ________
a) 1 coil
b) 4 coils
c) 3 coils
d) 10 coils

View Answer

Answer: c [Reason:] The moving element of an ohmmeter in a megger consists of three coils, namely current or deflection coil, pressure or control coil and compensating coil.

9. The role of the compensating coil in a megger is ________
a) reduce current
b) increase voltage
c) control temperature
d) scaling

View Answer

Answer: d [Reason:] Temperature is controlled by minimising the flow of current through the circuit. Better scaling proportions can be achieved in a megger by making use of a compensating coil.

Set 4

1. Multichannel data acquisition system has
a) multiple channels
b) single channel
c) two channels
d) five channels

View Answer

Answer: a [Reason:] A multichannel data acquisition system has multiple channels. The various subsystems can be shared in terms of time by more than two or more input sources.

2. How many types of multiplexed system exist?
a) 2
b) 3
c) 5
d) 10

View Answer

Answer: b [Reason:] In general there are three types of multiplexed systems. They are as follows: • Multichannel Analog Multiplexed System • Multiplexing Output of Sample/Hold Circuits • Multiplexing after A/D Conversion.

3. Multichannel Analog Multiplexed System is
a) very fast
b) fast
c) slow
d) moderate

View Answer

Answer: c [Reason:] The Multichannel Analog Multiplexed System is one type of multiplexed system. It is comparatively slow. As it shares more than one channel, the cost is less.

4. Multichannel Analog Multiplexed System utilises time
a) using a transformer
b) using a capacitor
c) using a flip-flop
d) using a mux

View Answer

Answer: d [Reason:] Multichannel Analog Multiplexed System is one type of multiplexed system. It makes use of a multiplexer (mux) to utilise the time. The previous data stored in the sample and hold circuit gets converted into digital form.

5. In a Multichannel Analog Multiplexed System
a) A/D converter is used
b) D/A converter is used
c) Sigma delta converter is used
d) Modulator is used

View Answer

Answer: a [Reason:] In a Multichannel Analog Multiplexed System, individual analog signals are applied directly. The signals are amplified and conditioned. An A/D converter then converts the signals into digital form.

6. In a Multichannel Analog Multiplexed System, data stored in sample and hold circuit is converted into analog form.
a) True
b) False

View Answer

Answer: b [Reason:] The Multichannel Analog Multiplexed System, converts the previous data stored in the sample and hold circuit into digital form. Upon data collection, mode of the sample and hold circuit is changed to hold mode.

7. Many channels can be monitored at the same time by
a) Demultiplexing
b) A/D conversion
c) Multiplexing
d) D/A conversion

View Answer

Answer: c [Reason:] Monitoring of a number of channels can be done at the same time by multiplexing the outputs of the sample and hold circuit.

8. Multiplexing after A/D conversion involves
a) noisy data
b) mixed signal data
c) analog data
d) digital data

View Answer

Answer: d [Reason:] Multiplexing after A/D conversion is also known as fast data acquisition. Digital data performs logical operation and depending on the relative speed, the scan rate can be increased or decreased.

9. Multiplexing after A/D conversion provides immunity to noise.
a) True
b) False

View Answer

Answer: a [Reason:] Multiplexing after A/D conversion involves the transformation of analog signal into digital form. Data transmission provides, immunity from line frequency and other interferences.

Set 5

1. A successive approximation type DVM makes use _______
a) of a digital divider
b) of an analog divider
c) of an oscillator
d) of a transducer

View Answer

Answer: a [Reason:] Servo balancing type DVM makes use of a linear divider in a potentiometer. In the case of a successive approximation type DVM we make use of a digital divider. A digital divider is basically a digital to analog converter.

2. Successive approximation type DVM is based on the principle of ______
a) acceleration of an object
b) weight of an object
c) velocity of an object
d) momentum of an object

View Answer

Answer: b [Reason:] A successive approximation type DVM works on the principle of measuring the weight of an object. It consists of an object on one of the sides of the balance and an appropriate weight on the other side of the balance. The weight of the object is determined by successively adding and removing weights from the balance.

3. Which compares the output in a successive approximation type DVM?
a) op amp
b) diode
c) comparator
d) rectifier

View Answer

Answer: c [Reason:] A comparator is used to compare the output of the digital to analog converter in a successive approximation type DVM. As a result the comparator provides high or low signals.

4. D/A converter generates the set pattern successively.
a) True
b) False

View Answer

Answer: a [Reason:] If the output of the digital to analog converter becomes equal to the unknown voltage in terms of magnitude, the D/A converter generates the set pattern of voltages successively.

5. What is the role of logic control and sequencer in a successive approximation type DVM?
a) generate analog voltage
b) generate power
c) generate current through resistance
d) generate sequence code

View Answer

Answer: d [Reason:] A comparator is used in a successive approximation type DVM so as to compare the output of the D/A converter with the unknown voltage. Logic control and sequencer takes the input from the comparator and generates the sequence code.

6. Resolution of a successive approximation type DVM is given by the relation.
a) R = 110n
b) R = 110
c) R =10n
d) R = 10

View Answer

Answer: a [Reason:] The resolution of a successive approximation type depends on the number of digits. It is given by the relation, R = 110n where, R is the resolution n is the number of digits.

7. Sensitivity of a successive approximation type DVM is given by the relation.
a) S = fsmin
b) S = fsmin × R
c) S = R
d) S = fsminR

View Answer

Answer: b [Reason:] In a successive approximation type DVM, the sensitivity is given by the relation b) S = fsmin × R where, S is the sensitivity R is the resolution fsmin is the full scale reading when the range is minimum.

8. Speed of a successive approximation type DVM can be improved by making use of ______
a) electrical switches
b) mechanical devices
c) solid state devices
d) transformers

View Answer

Answer: c [Reason:] Solid state devices can be used in order to increase the speed of operation in a successive approximation type DVM. Electromechanical switches provide a low speed of operation.

9. Accuracy depends on external supply.
a) True
b) False

View Answer

Answer: b [Reason:] In a successive approximation type DVM, the accuracy is dependent on the internal reference supply. It also depends on the accuracy of the digital to analog converter that is used in the circuit.