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Multiple choice question for engineering

Set 1

1. Active transducers are classified into
a) 4 types
b) 2 types
c) 6 types
d) 8 types

View Answer

Answer: a [Reason:] Active transducers can be subdivided into four types. They are as follows: • Photovoltaic • Thermoelectric • Piezoelectric • Electromagnetic.

2. Active transducers develop
a) mechanical parameter
b) electrical parameter
c) chemical parameter
d) physical parameter

View Answer

Answer: b [Reason:] Active transducers are also known as self generating type of transducers. They develop an electrical voltage or current proportional to the quantity being measured.

3. How do passive transducers develop electrical signals?
a) using a transformer
b) using internal source
c) using external source
d) using a diode

View Answer

Answer: c [Reason:] Passive transducers develop electrical signals by means of an external source. They are usually known as externally power driven sources.

4. Capacitive transduction involves
a) change in resistance
b) change in inductance
c) change in resistance
d) change in capacitance

View Answer

Answer: d [Reason:] In capacitive transduction, measurand involves the change in the capacitance. Capacitance changes when the distance between the plates is varied or by a change in the dielectric.

5. In electromagnetic based transduction measurand is
a) converted into mechanical force
b) converted into electromotive force
c) converted into chemical force
d) converted into physical force

View Answer

Answer: b [Reason:] Electromagnetic transduction involves the conversion of the measurand into electromotive force. Magnetic flux is produced as a result of the relative motion between the magnet and an electromagnet.

6. Inductive transduction involves
a) change in self inductance
b) change in capacitance
c) change in mutual inductance
d) change in resistance

View Answer

Answer: a [Reason:] In an inductive transduction based system, measurand involves change in the self inductance of the coil.

7. Photovoltaic transduction involves
a) voltage generation heat
b) voltage generation through sound
c) voltage generation through light
d) voltage generation current

View Answer

Answer: c [Reason:] In a photovoltaic transduction based system, measurand is converted into voltage when the junction between dissimilar elements is illuminated.

8. Analog transducers convert input into
a) voltage
b) current
c) digital
d) analog

View Answer

Answer: d [Reason:] The analog transducers convert input into analog signal. The output is a continuous function of time. Strain gauge, LVDT, thermistor etc are analog transducers as they produce outputs which are a continuous function of time.

9. Inverse transducer converts electrical into a physical quantity.
a) True
b) False

View Answer

Answer: a [Reason:] An inverse transducer is used to convert an electrical quantity into a physical quantity. For example loudspeaker converts electrical signal into sound signal.

10. Digital transducers produce analog output.
a) True
b) False

View Answer

Answer: b [Reason:] Digital transducers produce digital output in response to an input signal. A unique code is generated for each discrete value sensed.

Set 2

1. By making use of a CRO _________
a) many characteristics of a signal can be measured
b) only a few characteristics of a signal can be measured
c) no characteristics of a signal can be measured
d) signal can only be displayed

View Answer

Answer: a [Reason:] Through the means of a Cathode Ray Oscilloscope, most of the characteristics of an input signal can be measured. Properties of a signal can be studied as well.

2. How is the waveform adjusted?
a) by adjusting the voltage
b) through shift controls
c) by reducing the current
d) by means of a galvanometer

View Answer

Answer: b [Reason:] In a Cathode Ray Oscilloscope, the waveform can be adjusted by means of shift controls. As a result, the measurement of divisions corresponding to the amplitude becomes easy.

3. How is error in measurement reduced?
a) using r.m.s value
b) using absolute value
c) using peak to peak value
d) using a voltmeter

View Answer

Answer: c [Reason:] In a Cathode Ray Oscilloscope, the error in measurement is reduced by making use of the peak to peak value.

4. Peak to peak voltage is given by ________
electrical-measurements-questions-answers-cro-measurements-q4

View Answer

Answer: d [Reason:] In a Cathode Ray Oscilloscope, the peak to peak voltage is given by the relation, Vp-p=number of units×(voltsdivision) where, Vp-p is the peak to peak voltage.

5. The amplitude of voltage is given by the relation.
electrical-measurements-questions-answers-cro-measurements-q5

View Answer

Answer: a [Reason:] In a Cathode Ray Oscilloscope, the amplitude of voltage is given by the relation, Vm = (Vp-p2) where, Vp-p is the peak to peak voltage Vm is the amplitude.

6. The R.M.S voltage is given by the relation
electrical-measurements-questions-answers-cro-measurements-q6

View Answer

Answer: b [Reason:] The r.m.s value of voltage is given by the relation, electrical-measurements-questions-answers-cro-measurements-q6a where, Vrms is the r.m.s value of voltage Vm is the amplitude of the voltage.

7. CRO is voltage measuring device.
a) True
b) False

View Answer

Answer: a [Reason:] Generally, a CRO is a voltage measuring device. Current is measured by passing current through a known value of resistance. Voltage across the resistance is displayed on the screen of the CRO.

8. Period of a waveform is obtained by the relation.
a) T=number of divisions occupied by 1 cycle×(time)
b) T=number of divisions occupied by 1 cycle×(1division)
c) T=number of divisions occupied by 1 cycle×(timedivision)
d) T=number of divisions occupied by 1 cycle

View Answer

Answer: c [Reason:] The time period of a waveform is obtained by using the relation, T=number of divisions occupied by 1 cycle×(timedivision).

9. How is frequency related to time period?
a) square proportional
b) not related
c) directly proportional
d) inversely proportional

View Answer

Answer: c [Reason:] Frequency is inversely proportional to the time period of any given signal. f = 1t where, f is the frequency T is the time period.

Set 3

1. CRO uses __________
a) 2 delay lines
b) 3 delay lines
c) 4 delay lines
d) 5 delay lines

View Answer

Answer: a [Reason:] Cathode Ray Oscilloscope uses two delay lines. They are as follows: Lumped parameter delay line and Distributed parameter delay line.

2. T section in a delay circuit of CRO acts as ________
a) high pass filter
b) low pass filter
c) band pass filter
d) band reject filter

View Answer

Answer: b [Reason:] In the delay circuit of a CRO, T section is present in the lumped parameter delay line. The T section acts as a low pass filter having a cut off frequency as, electrical-measurements-questions-answers-delay-line-q2.

3. Lumped parameter delay line consists of________
a) RC networks
b) RL networks
c) LC networks
d) Resistive networks

View Answer

Answer: c [Reason:] In the delay line circuit of a Cathode Ray Oscilloscope, the lumped parameter delay line is made of several cascaded LC networks. They are known as T sections.

4. Delay for the T section is given by ________
a) ts = 1fc
b) ts = 1
c) ts = 1π
d) ts = 1πfc

View Answer

Answer: d [Reason:] In the T section of the lumped parameter delay in a delay line circuit of the CRO the delay is given by the relation ts = 1πfc ts = delay for a single circuit td = total delay n = number of T sections.

5. Distributed parameter delay line is a transmission line.
a) True
b) False

View Answer

Answer: a [Reason:] The delay line circuit consists of distributed parameter delay as well as lumped parameter delay. The distributed parameter delay is basically a transmission line with a coil wound on a helix mandrel.

6. Inductance does not affect a transmission line?
a) True
b) False

View Answer

Answer: b [Reason:] The inductance of the transmission line in a distributed parameter delay line can be increased by winding the inner conductor of the helix onto a ferromagnetic core.

7. Typical values for a distributed parameter delay line are ________
a) Zo = 10 Mῼ and td = 10 nsec/m
b) Zo = 1 kῼ and td = 500 nsec/m
c) Zo = 1000 ῼ and td = 180 nsec/m
d) Zo = 100 Gῼ and td = 275 nsec/m

View Answer

Answer: c [Reason:] For the distributed parameter delay line in a delay line circuit the typical parameters are the characteristic impedance which is Zo = 1000 ῼ and the delay time which is td = 180 nsec/m.

8. What is the effect of the signal delay on the sweep generator?
a) no effect
b) input increases in magnitude
c) output doesn’t get any delay
d) output gets sufficient delay

View Answer

Answer: d [Reason:] When the signal is delayed, the sweep generator’s output gets sufficient time in order to reach the horizontal plates before the signal passes over to the vertical deflection plates.

Set 4

1. The secondary leakage reactance of a C.T.
a) increases its ratio error
b) decreases its ratio error
c) has no effect on its ratio error
d) increases the impedance of the circuit

View Answer

Answer: a [Reason:] The windings in a current transformer must be kept close so that the secondary leakage reactance is minimum. Secondary leakage reactance of a C.T. thus increases its ratio error.

2. Secondary and primary windings consist of ________
a) copper turns
b) 14 S.W.G copper wire and copper strip respectively
c) iron coils wound around
d) laminations

View Answer

Answer: b [Reason:] For a current transformer the most popular form used is the bar primary and ring core construction. Hence 14 S.W.G copper wire is used for the secondary winding whereas a copper strip is used for the primary winding.

3. Coils of a C.T. are separately wound.
a) True
b) False

View Answer

Answer: a [Reason:] A C.T. is used for the measurement of high magnitudes of current. In order to get lower line voltages, the coils of a C.T. are wound separately and insulated through tapes and varnish.

4. The windings of a C.T. are ________
a) tied together
b) shorted
c) wound over one another
d) grounded

View Answer

Answer: c [Reason:] Using cylinders made of Bakelite, the windings of a C.T. are wound over one another. This setup is mounted on a steel tank sheet filled with transformer oil.

5. At high voltages, the current transformers are enclosed in a tank.
a) True
b) False

View Answer

Answer: a [Reason:] The current transformers are enclosed in a tank at high voltages of the order of more than 7 kV. The tank consists of a solid insulating compound. Since the cooling is poor, the compound introduces difficulty.

6. Turns compensation is used to obtain ________
a) to compensate the turns
b) to equalise the turns on the windings
c) to protect the equipment
d) transformation ratio equal to nominal ratio

View Answer

Answer: d [Reason:] In a C.T., the transformation ratio is given by R = n + IeIs where, n is the turns ratio Ie is the core loss component of the excitation current Is is the secondary winding current Turns compensation is used to obtain the transformation ratio (R) equal to the nominal ratio (Kn).

7. What is the effect of reducing the secondary turns in a C.T. by 1%?
a) transformation ratio reduces by the same value
b) no effect
c) nominal ratio increase by the same value
d) secondary current increases by the same value

View Answer

Answer: a [Reason:] In a C.T., the transformation ratio is given by R = n + IeIs where, n is the turns ratio Ie is the core loss component of the excitation current Is is the secondary winding current As the number of secondary turns is reduced by a factor of 1%, the transformation ratio (R) is reduced by approximately the same percentage.

8. In a 1000/5 A C.T., the number of secondary turns would be ________
a) 200
b) 199 or 198
c) 5
d) 1000

View Answer

Answer: b [Reason:] The optimum number of secondary turns in a C.T. is the value that makes the transformation ratio (R) and nominal ratio (Kn) equal. It is usually one or two turns less than the actual value. Thus in a 1000/5 A, though the number of turns would be 200 ideally, it is considered as 198 or 199 in order to keep R and Kn equal.

9. In the ring type of core, the secondary winding is ________
a) non-uniformly distributed over the core
b) shorted with the primary winding
c) uniformly distributed over the core
d) connected in the form of a ring

View Answer

Answer: c [Reason:] The ring type of core used for a secondary winding is a jointless core. It has a very small leakage reactance. Hence in a ring type of core, the secondary winding is uniformly distributed over the core.

10. In a shell type of core, the windings are ________
a) in the form of the a shell
b) shorted with the primary windings
c) not wound
d) placed on the central limb

View Answer

Answer: d [Reason:] The windings in a shell type of core are placed in a central limb. It provides protection to the windings.

11. Mumetal has ________
a) low permeability, high loss
b) high permeability, medium loss
c) medium permeability, high loss
d) high permeability, low loss

View Answer

Answer: c [Reason:] Mumetal is an alloy of nickel, iron and copper. It has a high permeability, low loss and small retentivity. It has a maximum permeability of 90,000 at a flux density of 0.35 W/m2.

12. Perminder has __________
a) medium saturation point of permeability
b) low saturation point of permeability
c) no saturation point of permeability
d) high saturation point of permeability

View Answer

Answer: d [Reason:] Perminder is an alloy of iron, cobalt and vanadium. It has a high flux density of the order of 2.4 Wb/m2. It is very expensive.

Set 5

1. A/D converter is used for __________
a) converting analog to digital
b) converting digital to analog
c) converting digital to mixed signal mode
d) converting analog to mixed signal mode

View Answer

Answer: a [Reason:] In a digital data acquisition system, an A/D converter is used for the purpose of converting analog signals to digital.

2. Output of A/D converter is _________
a) given to an analog display
b) given to a digital display
c) given to a CRO
d) given to an voltmeter

View Answer

Answer: b [Reason:] Output from the analog to digital converter is given to a digital display device or to a digital recorder for the purpose of displaying or recording.

3. What are auxiliary equipments?
a) equipments
b) guard rings
c) devices
d) voltage source

View Answer

Answer: c [Reason:] Auxiliary equipments are basically devices used for system programming functions and digital data processing applications.

4. What is the main function of auxiliary equipment?
a) unit step response
b) ramp response
c) non-linear response
d) linear response

View Answer

Answer: d [Reason:] The typical functions of auxiliary equipments include linearization and limit compression for the input signals. Individual instruments or a digital computer is used to perform these functions.

5. What is a digital recorder?
a) records digital data
b) records analog data
c) does not record data
d) records both analog and digital data

View Answer

Answer: a [Reason:] A digital recorder is used for the purpose of recording the digital data. Punched cards, magnetic tape recorders, type written pages, etc make use of digital recorders.

6. Data acquisition systems are not widely used.
a) True
b) False

View Answer

Answer: b [Reason:] In digital recorders, data acquisition systems are used widely in industries, space applications, medical and telephony.

7. For lower accuracies _________
a) digital acquisition system is used
b) both digital and analog acquisition systems are used
c) analog acquisition system is used
d) mechanical data acquisition system is sued

View Answer

Answer: c [Reason:] When low values of accuracy is required, analog data acquisition system is used. This includes a wide frequency bandwidth as well.

8. Digital acquisition systems are used when _________
a) bandwidth is high
b) bandwidth is medium
c) bandwidth is zero
d) bandwidth is low

View Answer

Answer: d [Reason:] When the bandwidth required is low, usually digital acquisition systems are made use of. For higher accuracy and lower per channel cost, digital data acquisition systems are used.