Multiple choice question for engineering
1. Thermoelectric transducer is a __________
a) temperature transducer
b) pressure transducer
c) inductive transducer
d) capacitive transducer
Answer: a [Reason:] A thermoelectric transducer is a temperature transducer. It converts thermal energy into electrical energy.
2. Commonly used thermoelectric transducer is
c) linear variable differential transducer
d) loud speaker
Answer: b [Reason:] 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
Answer: c [Reason:] 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 [Reason:] 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.
Answer: a [Reason:] 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 [Reason:] 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 ________
Answer: c [Reason:] 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.
Answer: b [Reason:] 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. 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 [Reason:] 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.
a) cold compensation is needed
b) hot compensation is needed
c) no compensation is needed
d) hot and cold compensations are needed
Answer: a [Reason:] Temperature can be measured accurately by using a thermocouple with cold junction temperature compensation.
1. Time domain oscilloscopes require ___________
a) sweep generator
Answer: a [Reason:] Time domain oscilloscopes need a sweep generator. The sweep generator must be a linear function of time for the x-axis display.
2. What is time base generator?
a) time measuring device
c) voltage generation device
d) current generation device
Answer: b [Reason:] In a Cathode Ray Oscilloscope, a generator that produces a waveform required for the movement of the visible spot horizontally is known as the time base generator.
3. Linear sweep moves spot __________
a) top to bottom
b) right to left
c) left to right
d) bottom to top
Answer: c [Reason:] In a Cathode Ray Oscilloscope, a linear sweep is used to move the visible spot from left to right direction. The movement of the spot from right to left direction is not visible.
4. Time base generator controls __________
a) intensity of light
b) current direction
c) voltage magnitude
d) spot movement
Answer: d [Reason:] In a Cathode Ray Oscilloscope, the time base generator controls the rate at which the visible spot moves across the screen. Using the front panel controls this rate can be modified.
5. Time dependent waveforms need x-axis for calibration.
Answer: a [Reason:] In a Cathode Ray Oscilloscope, the time dependent waveforms need x-axis for calibration. It is calibrated as the time axis.
6. Sweep generator works on the principle of __________
Answer: b [Reason:] In a Cathode Ray Oscilloscope, the sweep generator basically works on the principle of a capacitor. It generates linear rise time voltages by making use of the charging characteristics of a capacitor.
7. Left to right visibility of the spot is ensured by __________
a) linear waveform
b) linear ramp waveform
c) sinusoidal waveform
d) unit step waveform
Answer: c [Reason:] In the time base generator, a linearly increasing ramp waveform that decreases to zero within a very short time span is used to make sure that the spot is only visible from left to right direction.
8. Time base generator circuit resembles a __________
Answer: d [Reason:] The time base generator circuit is basically a relaxation oscillator. It generates a saw tooth waveform. A bootstrap technique allows linearity but is very expensive.
9. Sweep generator is a time base generator.
Answer: a [Reason:] In a Cathode Ray Oscilloscope the sweep base generator produces the movement of the spot on the screen. It acts as the time base for the waveforms and as a result it is known as a time base generator.
1. Selection of a transducer depends on the quantity being measured.
Answer: a [Reason:] A transducer is selected based on the nature of the quantity that is being measured. For example temperature measurement involves the use of temperature sensors whereas measurement of stress involves a strain gauge.
2. A transducer must have
a) maximum loading
b) minimum loading
c) zero loading
d) infinite loading
Answer: b [Reason:] A transducer in general should have a minimum amount of load. Minimum loading effect ensures that the transducer has minimal errors in the measurement of any quantity.
3. Transducers must operate under
a) zero electromagnetic field
b) constant electromagnetic fields
c) varying electromagnetic fields
d) infinite electromagnetic field
Answer: c [Reason:] A transducer should operate under strong electromagnetic fields. Generally transducers with a low value of output impedance, high value of output voltage and shorter cable length are not susceptible to such interference.
4. Errors can be minimised in some transducers through
a) power compensation
b) voltage compensation
c) resistance compensation
d) temperature compensation
Answer: d [Reason:] In some transducers errors occurring due to temperature changes can be minimized by providing temperature compensation. Operation and maintenance of transducers beyond 300°F is extremely difficult.
5. How can a transducer be used in environment with vibrations?
a) using shock absorbers
b) using proper grounding
c) using effective voltage
d) using a transformer
Answer: a [Reason:] Transducers can be used effectively in an environment subjected to shock and vibrations by making use of dampers.
6. How many passive transducers are there?
Answer: b [Reason:] There are three passive transducers. They are as follows:
7. Resistance of a metallic conductor is given by
a) R = I⁄A
b) R = ρ⁄A
c) R = ρl⁄A
d) R = 1⁄A
Answer: c [Reason:] The resistance of a metallic conductor is given by the relation
R = ρl⁄A where, R is the resistance
l is the length
A is the area of cross-section
ρ is the resistivity of material of the conductor.
8. Passive transducers are described with their primary parameters.
Answer: a [Reason:] The passive transducers such as resistor, capacitor and inductor are described through the means of their primary parameters namely resistance, capacitance and self inductance.
9. Rotational potentiometers use
b) self inductance
c) mutual inductance
Answer: d [Reason:] Rotational potentiometers or translational potentiometers make use of the change in resistance as a result of the change in length of a conductor.
10. Temperature transducers make use of
a) change in resistivity
b) change in length
c) change in area
d) change in capacitance
Answer: a [Reason:] The change in resistivity of the material of a conductor is used to measure the variation in temperature. Temperature is affected due to change in the resistance which in turn varies the resistivity.
1. How many types of transducers are there?
Answer: a [Reason:] There are basically two types of transducers. They are as follows:
2. Mechanical transducers sense __________
a) electrical changes
b) physical changes
c) chemical changes
d) biological changes
Answer: b [Reason:] A mechanical transducer senses the changes in a system’s physical condition and gives an output. When a bimetallic strip is subjected to changes in temperature, the output is the displacement of the strip mechanically.
3. Mechanical transducers generate ________
a) electrical signals
b) chemical signals
c) physical signals
d) biological signals
Answer: c [Reason:] Mechanical transducers in general portray physical or mechanical signals at the output in response to any physical changes in a system.
4. Electrical transducers generate ________
a) biological signals
b) chemical signals
c) physical signals
d) electrical signals
Answer: d [Reason:] Electrical transducers in general respond to physical quantities which are non-electrical such as pressure, temperature, force etc and generate equivalent electrical signals at their output.
5. Electrical signals are easy to amplify.
Answer: a [Reason:] Electrical signals are easier to either amplify or attenuate. By making use of static devices such as FGK, electrical signals can be brought to a suitable level.
6. The power needs of electrical transducers is ________
Answer: b [Reason:] Electrical transducers have very minimum power requirements. Electrical transducer based systems are controlled with a small amount of power.
7. Electrical transducers are ________
a) small and non-portable
b) large and non-portable
c) small and compact
d) large and portable
Answer: c [Reason:] Electrical systems have integrated circuits which are small and compact. They can be easily ported as well.
8. Mechanical transducers cause ________
a) power loss
b) hysteresis loss
c) eddy current loss
d) frictional loss
Answer: d [Reason:] Mechanical transducer based systems are affected by the frictional loss of the rotating parts. In electrical transducers, there is no wear and tear due to non moving parts.
9. Electrical transducers are costly.
Answer: a [Reason:] Electrical transducers are very expensive in nature. The ageing and drift of the various electronic components acts as an overhead in the use of electrical transducers on a large scale.
1. R.M.S value means _________
a) root mean square
b) rate mean second
c) root median second
d) rate mode second
Answer: a [Reason:] R.M.S value indicates the Root Mean Square. It is obtained by taking the square root of the average value of the square of the input signal. It is also known as the effective value.
2. Meter reading is obtained by ________
a) sensing voltage
b) sensing heat power
c) sensing current
d) sensing resistance
Answer: b [Reason:] In a true R.M.S responding voltmeter, the meter reading is obtained by sensing the heat power of the waveform. The heat power is directly proportional to the r.m.s value of the input.
3. Measurement of heat power ________
a) uses a heat sink
b) uses a thermometer
c) uses a thermocouple
d) uses a black body
Answer: c [Reason:] A thermocouple is used to measure the heat power in a true R.M.S responding voltmeter. Input voltage under measurement is applied to the heater to which a thermocouple is also attached.
4. Sufficient heating of the heater is ensured by ________
a) increasing the temperature
b) making use of induction coil
c) amplifying d.c. input
d) amplifying a.c. input
Answer: d [Reason:] Maximum heating of the heater is obtained by making use of an amplified a.c. input. As a result the thermocouple generates maximum voltage level in order to cause the meter deflection.
5. Power in a thermocouple is given by ________
a) Power = E2 rms / Rheater
b) Power = E2 rms
c) Power = Rheater
d) Power =E2 rms × Rheater
Answer: a [Reason:] The power consumed in a thermocouple is given by the relation
Power = E2 rms ⁄ Rheater where, Erms is the r.m.s value of the a.c. input signal
Rheater is the resistance of the heater.
6. Main disadvantage of a true r.m.s responding voltmeter is ________
a) presence of transducer
b) presence of thermocouple
c) presence of transformer
d) presence of oscillator
Answer: b [Reason:] Thermocouples have non-linear voltage and current characteristics. This is the major drawback of the true r.m.s responding voltmeter. This is overcome in some instruments by making use of an additional thermocouple in the same thermal environment.
7. What is the naming convention for the two thermocouples?
a) thermocouple 1 and thermocouple 2
b) input thermocouple and output thermocouple
c) measuring thermocouple and balancing thermocouple
d) internal thermocouple and external thermocouple
Answer: c [Reason:] The thermocouple used in the input section of the voltmeter is known as the measuring thermocouple whereas the thermocouple used in the feedback path is known as the balancing thermocouple.
8. Sensitivity is of the order of ________
Answer: d [Reason:] By making use of true r.m.s responding voltmeter we get sensitivity of the order of mV. The voltage ranges from 100 µV to 300 V with a frequency range of 10 Hz to 100 MHz.
9. Response of thermocouples is fast.
Answer: b [Reason:] Crest factor limits the meter reading in a true r.m.s responding voltmeter when complex signals are taken into consideration. Also the meter costs higher compared to average and peak responding meters. As a result the response of the thermocouples is slow.