Multiple choice question for engineering
1. Transducer is used to convert a _________
a) physical quantity into an electrical signal
b) electrical signal into a physical quantity
c) physical quantity into a mechanical quantity
d) physical quantity into a chemical quantity
Answer: a [Reason:] Transducer forms one of the most important components of an analog data acquisition system. It converts a physical quantity into an electrical signal. Strain gauge, thermocouples, piezoelectric devices are the most widely used transducers.
2. Transducer produces a _________
a) proportional current
b) proportional voltage
c) proportional resistance
d) proportional power
Answer: b [Reason:] A transducer generates a voltage proportional to the physical quantity that is being measured. The voltage output from a transducer forms the input to a data acquisition system.
3. Sensors produce frequency which is counted by _________
a) a chemical counter
b) a mechanical counter
c) an electronic counter
d) a basic counter
Answer: c [Reason:] Transducers consist of special sensors used to produce frequency that can be counted by means of an electronic counter. This frequency forms an integral part of the frequency measured.
4. Signal conditioner is used for _________
a) attenuating the voltage
b) maintaining a constant voltage
c) keeping the voltage zero
d) boosting the voltage
Answer: d [Reason:] Signal conditioner is an important part of an analog data acquisition system. A signal conditioner converts the output voltage to the desired form which is accepted by the next stage.
5. A multiplexer is used for _________
a) accepting multiple inputs
b) accepting single input
c) accepting multiple outputs
d) accepting single output
Answer: a [Reason:] A multiplexer forms an important constituent of an analog data acquisition system. It takes multiple analog inputs. By making use of a multiplexer many quantities can be transmitted.
6. Multiplexers are used when the distance between source and destination is less.
Answer: b [Reason:] Generally multiplexers are made use of only when the distance of separation between the transmitting end and the receiving end is more.
7. Output signal is captured using _________
Answer: c [Reason:] In a analog data acquisition system, the output signal is recorded by means of an analog recorder. It includes the likes of strip chart recorder, magnetic tape recorder etc.
8. Analog computers have __________
a) zero cost
b) intermediate cost
c) more cost
d) less cost
Answer: d [Reason:] The accuracy of digital computers is more than that of analog computers. Analog computers are widely used when compared to digital computers because of their less cost.
9. Before and after each test, calibration is carried out.
Answer: a [Reason:] In an analog data acquisition system, calibration carried out before each test is known as pre-calibration. The test carried out after calibration is known as post-calibration.
1. CRO is used for measurement of __________
a) AC as well as DC current
b) AC current only
c) DC current only
d) AC power only
Answer: a [Reason:] A Cathode Ray Oscilloscope is used for the measurement of AC as well as DC current. It is used for the calculation peak to peak voltage, r.m.s value, duty cycle etc.
2. CRO is used in a radar for __________
a) studying the pattern of flights
b) visualizing a target
c) measuring voltage
d) determining the distance between source and destination
Answer: b [Reason:] A Cathode Ray Oscilloscope is used in a radar for visualizing a target such as an aeroplane, ship etc.
3. In radio applications, CRO is used for measuring __________
a) audio frequency range
b) a narrow range of frequencies
c) a wide range of frequencies
d) radio frequency range
Answer: c [Reason:] By making use of a Cathode Ray Oscilloscope, a wide range of frequencies can be measured. The radio frequency, audio frequency and intermediate frequency signals can be measured by making use of a CRO.
4. In medical applications CRO can be used for __________
a) measuring the heart beats
b) monitoring the brain
c) improving the nervous system functioning
d) displaying cardiograms
Answer: d [Reason:] A Cathode Ray Oscilloscope, can be used in medical applications for displaying cardiograms. Cardiograms are used for diagnosing the condition of heart of a patient. Electromyograms are used for studying the condition of a patient’s muscle.
5. CRO is used for many purposes in the industry.
Answer: a [Reason:] A Cathode Ray Oscilloscope, is used for observing B-H curves, P-V diagrams etc. A CRO is also used in various transducers for the measurement of strain, pressure and temperature.
6. A CRO can’t be used in transmission lines.
Answer: b [Reason:] A Cathode Ray Oscilloscope, is used in transmission lines for the measurement of modulation characteristics. It is also used for detecting the standing waves in a transmission line.
7. Curve tracers use CRO in __________
b) passive devices
c) active devices
d) op amps
Answer: c [Reason:] Curve tracers in a Cathode Ray Oscilloscope are used for testing active devices such as vacuum tubes, transistors and integrated circuits.
8. A CRO is used in check __________
a) op amps
d) capacitance, inductance and diodes
Answer: d [Reason:] A Cathode Ray Oscilloscope is used for checking diodes. It is also used in the measurement of inductances and capacitances. A CRO can also be used for detecting the faults in a circuit.
9. A CRO is used in labs for __________
a) frequency measurement
b) voltage measurement
c) current measurement
d) resistance measurement
Answer: a [Reason:] A Cathode Ray Oscilloscope is used in the laboratory for the measurement of frequency, phase and period of a signal. The periodic as well as non-periodic relationships of signals can also be studied.
1. What is earthing?
a) connecting electrical machines to earth
b) providing a connection to the ground
c) connecting the electrical machines to source
d) providing a source of current
Answer: a [Reason:] Connecting electrical machines to the general mass of the earth by making use of a conducting material with very low resistance is known as earthing.
2. What is an earth electrode?
a) electrode that is connected to earth
b) material used for earthing
c) electrode connected to the circuit
d) electrode which is connected to the mains
Answer: b [Reason:] Electrode connected to the main is basically a source of e.m.f. Conducting material that is used for connecting electrical machinery to the earth is known as an earth electrode.
3. Earth electrode provides ____________
a) high resistance
b) medium resistance
c) low resistance
d) very high resistance
Answer: c [Reason:] In the case of occurrence of any leakage currents due to poor shielding of the apparatus, the earth electrode is used to provide a very low resistance path from the electrical appliances to the earth.
4. How is the condition of an earth electrode measured?
a) by measuring the voltage
b) by measuring the current
c) by measuring the power
d) by measuring resistance
Answer: d [Reason:] The resistance of the earth electrode is measured in order to check whether it is in a good condition or not.
5. In a three phase system, the neutral is _________
b) connected to low voltage
c) connected to high voltage
d) not connected
Answer: a [Reason:] Earthing can be used to maintain a constant line voltage in a three phase system. This is achieved by earthing the neutral.
6. Earthing is used as return conductor in telephone lines and for traction work.
Answer: a [Reason:] The complications involved in laying separate telephone cables and the cast used for traction work is minimised. As a result earthing is used as a return conductor in telephone lines and for traction work.
7. Earthing does not help in protecting the equipment.
Answer: b [Reason:] Spike voltages occurring as a result of lightning or any other fault can be dissipated to ground by earthing, thus protecting the equipment.
8. After earthing, the different parts of an electrical machinery are at _________
a) infinite potential
b) intermediate potential
c) zero potential
d) undefined potential
Answer: c [Reason:] After earthing, the various parts of electrical machinery such as casing, armouring of cables, etc are at zero potential.
9. Connection of the various parts of a circuit to earth has a
a) medium resistance
b) high resistance
c) very high resistance
d) very low resistance
Answer: d [Reason:] Once an electrical apparatus is grounded, most of its components are at ground potential. When the different parts of an electrical machinery are connected to ground, they possess very low resistance.
10. Specific resistance of soil is _________
a) changes from soil to soil
b) is constant
c) depends on the circuit connected to it
d) depends on the supply voltage
Answer: a [Reason:] Specific resistance depends on the nature and properties of a material. Specific resistance is different for various types of soils such as dry soil, rocky soil, wet soil, etc.
1. Autoranging means __________
a) automatic ranging
b) fixed ranging
c) automobile ranging
d) constant ranging
Answer: a [Reason:] Autoranging refers to obtaining an automatic reading with optimum resolution under all operating conditions. Say for example, 155 mV is displayed as 155.0 and not 0.155.
2. A 3 digit display DVM with a maximum reading of 1999 indicates
a) increase by a factor
b) reduction by a factor
c) no change in value
d) depends on the circuit components
Answer: b [Reason:] A 3 digit display DVM with maximum reading capability indicates that any reading above the maximum set limit of 1999 will be reduced by a factor of 10.
3. For a value less than 0200, the instrument should ________
a) read values less than 0200 correctly
b) read values randomly
c) automatically switch range
d) should not respond at all
Answer: c [Reason:] The DVM should automatically switch its range when the display is greater than 1999 units as it is the maximum set limit for achieving a higher sensitivity.
4. ADC counter ________
a) attenuates the signal
b) converts digital to analog
c) converts analog to digital
d) contains information
Answer: d [Reason:] When the count produced by the ADC counter is less than 170, a control pulse is obtained for down ranging. Whereas the control pulse for up ranging is produced once the ADC counter exceeds 1999 units.
5. ADC gives polarity indication.
Answer: a [Reason:] ADC contains information required for polarity indication. The polarity of the signal that is integrated is of utmost importance.
6. Integration period is obtained by ________
a) using signal amplitude
b) counting the pulse
c) measuring time
d) by differentiating the signal
Answer: b [Reason:] By counting the pulses we obtain the integration period. Polarity measurement is obtained by making use of the last count or some of the last counts.
7. Integrator’s output is ________
a) attenuated through a filter
b) feedback to the input
c) stored in a flip-flop
Answer: c [Reason:] The output from integrator is used to set a polarity flip-flop. The flip-flop’s output is then stored in memory until the next measurement of voltage is obtained.
8. Old information is used to set range relays.
Answer: b [Reason:] Range relays are set through the decoder using the new information obtained with the help of a clock pulse. Decimal point is also changed as per the requirement of the new range.
1. Low voltage signals can be measured by ___________
Answer: a [Reason:] Electronic voltmeters make use of amplifiers to measure low voltage signals. It consists of two or more stages of D.C. amplifiers.
2. Input impedance of an electronic voltmeter is ________
Answer: b [Reason:] In an electronic voltmeter, the input impedance is maintained very high. This is achieved by making use of an FET (Field Effect Transistor) at the input of an electronic voltmeter.
3. Meter can be isolated from the circuit in a basic D.C. electronic voltmeter.
Answer: a [Reason:] Field effect transistor (FET) acts as a source follower and provides very high input impedance. BJT along with resistors form a balanced bridge circuit. As a result the meter circuit can be isolated from the main circuit.
4. Bridge is balanced by ________
c) zero adjustment resistor
d) head phone
Answer: c [Reason:] Bridge circuit in a basic D.C. electronic voltmeter is balanced by making use of a zero adjustment resistor such that the pointer shows zero deflection.
5. What is the effect of the input on the transistor Q2?
a) bias on Q2 decreases
b) bias on Q2 is constant
c) bias on Q2 is zero
d) bias on Q2 increases
Answer: d [Reason:] The bias on the transistor Q2 increases when the input voltage is applied. As a result a proportional amount of current flows through the meter. Hence the deflection of the meter is directly proportional to the applied voltage within the dynamic range.
6. What is basic range of a meter?
a) causes maximum deflection
b) causes minimum deflection
c) causes zero deflection
d) causes medium deflection
Answer: a [Reason:] The input voltage that causes maximum deflection of the meter is known as the basic range of a meter. It occupies the lowest range on the range switch in the unamplified circuits.
7. High range can be obtained in a basic D.C. electronic voltmeter by
a) a transformer
b) an attenuator
c) a transducer
d) a resistor
Answer: b [Reason:] By making use of an attenuator in a basic D.C. electronic voltmeter, we get high range of values for the voltage reading. Attenuator is basically a voltage divider circuit with a predefined front panel.
8. Sensitivity of electronic voltmeter is high.
Answer: a [Reason:] In a PMMC voltmeter (Permanent Magnet Moving Coil), the sensitivity obtained is less and of the order of a few volts. In electronic voltmeters the sensitivity is very high and is of the order of at least 100 times as that compared to a PMMC voltmeter.
9. Overloading is ________
a) damages the meter
b) increases the temperature
c) doesn’t affect the meter
d) decreases the sensitivity
Answer: c [Reason:] As transistors saturate after a certain range of operating voltage and current, the value of the meter current is limited. As a result, overloading does not affect the meter and it remains safe.