31 + Interview Questions in Automotive Electronics in Automobile Engineering Page 1 InterviewSolution

1.	Which of the following relation between indicated mean effective pressure (imep), brake mean effective pressure (bmep) and friction mean effective power (fmep) is correct?(a) imep = fmep + bmep(b) imep = fmep * bmep(c) imep = fmep – bmep(d) imep = fmep / bmepThis question was posed to me in unit test.My enquiry is from Performance Parameters and Characteristics in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct answer is (a) IMEP = fmep + BMEP Easy explanation: INDICATED mean effective pressure (imep) considered to be CONSISTS of the BRAKE mean effective pressure (bmep) and the friction mean effective pressure (fmep).

Discussion

2.	On which of the following does brake mean effective pressure (BMEP) in an engine depend upon?(a) Speed and torque(b) Speed and power(c) Torque(d) SpeedThis question was posed to me in examination.This intriguing question originated from Measurements and Testing in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct option is (b) SPEED and POWER To explain I would say: Brake power = 2πNT / 60000 where N =engine speed in RPM and T = torque in Nm. The dynamometers give the engine torque from which the brake power can be calculated. Thus the brake mean effective pressure in an engine DEPENDS on torque only. Also, Brake power = PmbLAn / 60000. Therefore, Pmb = kT where k = 2π / LA and k = 4π / L*A where L = stroke LENGTH, A = cross-sectional area of the cylinder, n = no. of working strokes per minute and, Pmb = brake mean effective pressure.

Discussion

3.	What can be obtained from the engine indicator diagram?(a) Indicated mean effective pressure(b) Brake mean effective pressure(c) Relative efficiency(d) Mechanical efficiencyThis question was addressed to me by my college director while I was bunking the class.I'm obligated to ask this question of Measurements and Testing in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct option is (a) Indicated MEAN effective pressure Easiest EXPLANATION: The ENGINE indicator diagram is USED to obtain the indicated mean effective pressure. Pressure-volume, P-V, and pressure-crank angle, P-θ is the two types of indicator diagram that can be obtained from an engine. Both these indicator DIAGRAMS are mutually convertible.

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4.	For which of the following the flame ionization detector (FID) is used to measure?(a) CO(b) HC(c) CO2(d) NOxThe question was asked in a national level competition.My question comes from Measurements and Testing topic in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right option is (B) HC To elaborate: Flame IONIZATION DETECTOR (FID) is USED to measure the hydrocarbon concentration. Ionization is the characteristic of HC compound.

Discussion

5.	What is the requirement of the air box in the airbox method of measuring airflow?(a) To dump out the pulsation(b) To provide the constant velocity of flow(c) To have a constant flow(d) To have a constant temperatureI have been asked this question during an interview for a job.The query is from Measurements and Testing in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» CORRECT answer is (a) To dump out the pulsation To explain I would SAY: The airbox is used to dump out the pulsation while measuring the airflow. In IC engines, the satisfactory measurement of the air consumption is difficult because the flow is PULSATING due to the cyclic nature of the engine and because the air is a COMPRESSIBLE fluid.

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6.	For which of the following the Chemiluminescence analyzer is used to measure?(a) NOx(b) CO(c) HC(d) CO2I have been asked this question in homework.This question is from Measurements and Testing topic in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right choice is (a) NOX To explain: The Chemiluminescence ANALYZER is used to measure NOx in the EXHAUST gases from the ENGINE. The principle of measurement is based on Chemiluminescence reaction between ozone and NO. It results in the formation of excited NO2.

Discussion

7.	The indicated power of the single-cylinder engine is 1.9 kW. It develops torque of 10 Nm at 1600 rpm. What is the friction power as the percentage of brake power?(a) 12.43%(b) 13.43%(c) 14.43%(d) 15.43%This question was posed to me in a national level competition.This question is from Performance Parameters and Characteristics in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct choice is (b) 13.43% Easiest explanation: Brake power = bp, Indicated power = ip = 1.9kW, FRICTION power = FP, SPEED = N = 1600 RPM, and torque = T = 10 NM. Brake power = bp = 2πNT / 60000 = 2π * 1600 * 10 / 60000 = 1.675 kW. Friction power = fp = ip – bp = 1.9 – 1.675 = 0.225 kW. Percentage loss = (fp / bp)100 = (0.225 / 1.675)100 = 13.43%.

Discussion

8.	To which of the following Morse test is applicable?(a) Single-cylinder SI engines(b) Single-cylinder CI engines(c) Multi-cylinder CI engines(d) Single and multi-cylinder SI and CI enginesI have been asked this question during an interview.My doubt stems from Measurements and Testing in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct option is (c) Multi-cylinder CI engines For EXPLANATION I WOULD say: The Morse test is USED to measure the indicated power (IP) from multi-cylinder CI engines. The test consists of obtaining the indicated power (IP) of the CI engines without any APPARATUS.

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9.	What does the Sankey diagram represent?(a) Torque vs speed(b) Heat balance of the engine(c) Air consumption vs speed(d) ηbth vs brake powerI have been asked this question in class test.Query is from Performance Parameters and Characteristics topic in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct CHOICE is (B) Heat BALANCE of the ENGINE The best explanation: Sankey diagram represents the heat balance sheet of the engine. In this diagram, the width of the stream represents the heat quantity being considered.

Discussion

10.	What is LVDT used to measure?(a) Gas temperature(b) Engine speed(c) Crank angle(d) Large displacementThis question was posed to me during a job interview.Question is taken from Engine Electronics in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct choice is (d) Large DISPLACEMENT Easiest explanation: LVDT is used to measure the large displacement. These are only used for the low-frequency measurements. These SENSORS are used to measure the parameters like VALVE lift etc.

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11.	What is volumetric efficiency?(a) A measure of the power of the engine(b) A measure of the speed of the engine(c) A measure of pressure rise in the cylinder(d) A measure of breathing capacity of the engineThis question was posed to me during an interview.I'd like to ask this question from Performance Parameters and Characteristics in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct option is (d) A MEASURE of breathing capacity of the engine Best explanation: VOLUMETRIC efficiency is the RATIO of the displaced volume of the fluid by the PISTON to the swept volume. It is the ratio of actual mass of air DRAWN by the engine to the theoretical mass which should be drawn by the engine.

Discussion

12.	What is the disadvantage of the piezoelectric pressure sensor?(a) It has too much sensitivity(b) It can measure only low pressure(c) It is not suitable for dynamic measurement(d) It can only give pressure differenceI had been asked this question during an internship interview.I'm obligated to ask this question of Engine Electronics topic in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct ANSWER is (d) It can only give pressure difference Easiest EXPLANATION: The DISADVANTAGE of the piezoelectric pressure sensor is that it can only give the pressure difference. The advantages of the piezoelectric pressure sensor are quick frequency response and they are of SMALL size.

Discussion

13.	What is mechanical efficiency?(a) The ratio of friction power to brake power(b) The ratio of the brake power to indicated power(c) The ratio of indicated power to friction power(d) The ratio of friction power to indicated powerThis question was addressed to me in an international level competition.This intriguing question comes from Performance Parameters and Characteristics topic in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct OPTION is (d) The ratio of FRICTION power to indicated power Best explanation: Mechanical efficiency is the ratio of friction power to indicated power. Mechanical efficiency takes into account the mechanical losses. The mechanical losses are DIVIDED into friction losses; power absorbed, VENTILATING action, and work of charging the cylinder.

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14.	What is the disadvantage of the piezoelectric pressure sensor?(a) It has too much sensitivity(b) It can measure only low pressure(c) It is not suitable for dynamic measurement(d) It can only give pressure differenceI got this question by my school teacher while I was bunking the class.This intriguing question originated from Engine Electronics in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer»

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15.	What is the use of the hot-wire sensor?(a) To measure temperature(b) To measure the smoke intensity(c) To measure the mass flow rate(d) To measure pressureThis question was posed to me during an interview for a job.My question is from Engine Electronics in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct choice is (c) To measure the mass flow rate Easiest EXPLANATION: The hot-wire SENSOR is USED to measure the mass flow rate. This sensor is positioned between the air filter and the THROTTLE VALVE.

Discussion

16.	Where are the electro-optical sensors used?(a) Position and speed measurement(b) Piston temperature measurement(c) Cooling water flow measurement(d) Lubricating oil flow measurementThe question was posed to me during an interview for a job.The above asked question is from Engine Electronics in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right answer is (a) Position and speed MEASUREMENT Easiest explanation: The electro-optical sensors can be used for position and speed measurement. These devices can operate on HIGH frequencies. ALSO, it can detect fast-moving OBJECTS.

Discussion

17.	Which of the following is the best method to measure the speed?(a) Mechanical tachometer(b) Electrical tachometer(c) Magnetic pickup(d) Mechanical countersI have been asked this question in a national level competition.This intriguing question originated from Measurements and Testing in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right option is (C) Magnetic pickup The BEST explanation: Magnetic pickup is the best device to measure the speed. MECHANICAL and electrical tachometers are AFFECTED by temperature VARIATION and those are not accurate.

Discussion

18.	The bore and stroke of the single-cylinder four-stroke engine are 90 mm and 120 mm respectively. The torque is 24 Nm. What is the brake mean effective pressure of the engine?(a) 3.9 bar(b) 4.9 bar(c) 5.9 bar(d) 6.9 barThe question was posed to me in an interview for job.This interesting question is from Performance Parameters and Characteristics topic in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct OPTION is (a) 3.9 bar Explanation: Brake mean EFFECTIVE pressure = PBM, torque = T = 24 Nm, stroke = L = 120 MM, bore = D = 90 mm. pbm = 16T / D^2L = (1624) / (0.090.090.12) = 3.9 10^5 Pa = 3.9 bar.

Discussion

19.	Which of the following is correct?(a) Thermal efficiency varies directly as specific fuel consumption(b) Thermal efficiency varies inversely as specific fuel consumption(c) Thermal efficiency varies as root as specific fuel consumption(d) Thermal efficiency varies as square as specific fuel consumptionI got this question during an interview.I need to ask this question from Performance Parameters and Characteristics in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct OPTION is (b) THERMAL efficiency varies inversely as SPECIFIC fuel consumption To explain: Specific fuel consumption is the ratio of fuel consumption rate to the power PRODUCED. Thermal efficiency is the ratio of the power produced to the fuel consumption rate. Hence both are inversely proportional to each other.

Discussion

20.	What is the use of the lambda sensors in the catalytic converter?(a) To keep excess air ratio within a range(b) To keep the flow rate of constant air(c) To keep the exhaust pressure constant(d) To keep the exhaust temperature constantThe question was posed to me during an online interview.This intriguing question originated from Engine Electronics topic in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right choice is (a) To keep excess air ratio within a RANGE Easy EXPLANATION: In CATALYTIC convertor, the lambda sensors are USED to keep excess air ratio within a range. The catalytic converter is the emission control DEVICE.

Discussion

21.	For which of the following the non-dispersive infra-red (NDIR) analyzer is used to measure?(a) CO2(b) CO(c) HC(d) NOxThis question was posed to me during a job interview.My question is from Measurements and Testing in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right OPTION is (b) CO To EXPLAIN I would SAY: Non-dispersive infra-red (NDIR) analyzer is used to measure CO. The method of detection is based on the principle of selective absorption of the infrared energy of particular wavelength unique to a CERTAIN gas which will be absorbed by that gas.

Discussion

22.	If the ip =2.62 kW and bp = 2.4 kW than fp = 5.04 kW(a) True(b) FalseI got this question in a national level competition.The above asked question is from Performance Parameters and Characteristics in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» RIGHT answer is (b) False Easy explanation: FRICTION power = fp, BRAKE power = bp = 2.4 KW, and INDICATED power = ip = 2.62 kW. ip = bp + fp ⇒ fp = ip – bp = 2.62 – 2.4 = 0.22 kW.

Discussion

23.	Which of the following is the most accurate dynamometer?(a) Eddy current dynamometer(b) Prony brake dynamometer(c) Hydraulic type dynamometer(d) Swinging field type dynamometerI had been asked this question in a national level competition.Question is taken from Measurements and Testing in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct ANSWER is (d) Swinging FIELD type dynamometer To explain I would SAY: Swinging field type dynamometer is the most accurate dynamometer. It consists of an electrical machine which MAY be run either by motor or generator.

Discussion

24.	Which of the following is the most accurate method of determining friction power?(a) Morse test(b) Willian’s line(c) Motoring test(d) Measurement of brake and indicated powerThe question was posed to me during an online exam.My question is from Measurements and Testing topic in section Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» CORRECT option is (d) MEASUREMENT of BRAKE and INDICATED power To explain: The friction power can be obtained by measurement of the brake and indicated power. The indicated power can be obtained by indicated diagram and brake power obtained by a dynamometer.

Discussion

25.	What is brake specific fuel consumption of engine whose fuel consumption if 6 grams per second and power output is 90 kW?(a) 0.24 kg/kWh(b) 0.0667 kg/kWh(c) 0.54 kg/kWh(d) 0.44 kg/kWhI have been asked this question in an international level competition.My question is from Performance Parameters and Characteristics topic in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The CORRECT CHOICE is (a) 0.24 kg/kWh Best EXPLANATION: Brake specific FUEL consumption = ṁf / bp where bp = brake power and ṁf = brake specific fuel consumption. Brake specific fuel consumption = 6 / 90 = 0.0667 g/kW-s = (0.0667 * 3600) / 1000 = 0.24 kg/kWh.

Discussion

26.	Vortex sensor is used for measurement of the temperature.(a) True(b) FalseI got this question by my college director while I was bunking the class.The question is from Engine Electronics topic in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» CORRECT CHOICE is (b) False To explain I would say: Vortex sensor is USED for measurement of the intake AIRFLOW. In this sensor, as the air PASSES the bluff body creates the vortex. Due to which pressure disturbances are created which can be sensed by the microphone.

Discussion

27.	In which of the following See beck effect is used?(a) Hot-wire sensors(b) Resistance temperature detectors(c) Thermocouples(d) ThermistorsThis question was addressed to me by my college professor while I was bunking the class.Origin of the question is Engine Electronics topic in division Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right ANSWER is (C) Thermocouples Easy explanation: Thermocouples USE the SEEBECK effect to measure the temperature. Thermocouples can be used for high-temperature measurement.

Discussion

28.	Which of the following is the knock sensor?(a) Flap type sensor(b) Thermocouples(c) Thermistors(d) Piezoelectric pickupThe question was asked in a job interview.The above asked question is from Engine Electronics topic in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» The correct OPTION is (d) Piezoelectric pickup Explanation: Piezoelectric pickup is the knock sensor. This sensor is MOUNTED on the CYLINDER block. Knock sensor system uses a sensor, which is piezoelectric VIBRATION pickup.

Discussion

29.	The Otto engine consumes 9 liters of petrol per hour and develops 30 kW. The specific gravity of petrol is 0.8 and its calorific value is 45000 kJ/kg. What is the indicated thermal efficiency of the engine?(a) 33.33%(b) 25%(c) 30%(d) 32%The question was posed to me in an interview for job.My question comes from Performance Parameters and Characteristics in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right option is (d) 32% The explanation: ηith = heat EQUIVALENT of indicated power / heat input = (30 * 60 * 60 * 100) / (910^-3800)*45000 = 33.33%.

Discussion

30.	Which of the following is used by the Hall Effect pickup?(a) Thermistors(b) Potentiometers(c) Inductive transducers(d) SemiconductorsI have been asked this question in quiz.The origin of the question is Engine Electronics in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Correct answer is (d) SEMICONDUCTORS The BEST I can explain: In Hall EFFECT pickup, semiconductors are used. This SENSOR used for detecting the position of the SHAFT and speed. This sensor can be used to detect motion.

Discussion

31.	What is the main use of the strain gauge?(a) To measure viscosity(b) To measure velocity(c) To measure temperature(d) To measure pressureI had been asked this question in an interview for job.I need to ask this question from Engine Electronics topic in portion Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering
Answer» Right ANSWER is (d) To measure pressure To explain: The main use of the strain GAUGE is to measure pressure.In this sensor, the conductor CHANGES the DIMENSION ALONG with the member whose strain is to be measured.

Discussion

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