## electrical

### Electrical Instruments MCQ Objective Questions and Answers Page - 5

1.
 Which one of the following statements is not correct  ? A Vacuum can act as a dielectric material B Piezoelectric materials can act as transducers C Quarz crystal is a ferroelectric material D The dielectric constant of dielectrics depends on the frequency of the applied field Answer : C Explanation :
2.
 Which one of the following pressure transducers is suitable for measurement of high pressure  ? A Alphatron B McLeod gauge C Pirani gauge D Bourdon gauge Answer : B Explanation :
3.
 Tachometers are used for only A Angular speed measurement B Linear speed measurement C Both angular and linear speed measurements D None of the above Answer : A Explanation :
4.
 The generated emf of a dc tacho-generator is A Directly proportional to angular speed B Inversely proportional to angular speed C Proportional to square root of angular speed D Proportional to square of angular speed Answer : A Explanation :
5.
 AC tachometers are often built with thin metallic drag-cup rotor to A Reduce inertia B Obtain low Q C Make them suitable for high frequency (400 Hz) operation D Eliminate direct coupling between two stator windings Answer : C Explanation :
6.
 Transducer for measurement of rotational displacement  is A Shaft recorder B Differential capacitor C LVDT D Strain gauge Answer : A Explanation :
7.
 An inductive pick-up used to measure the speed of a shaft has 120 tooth wheel. If the number of pules produced in a second is 3000, the rpm of the shaft is A 1200 B 1500 C 1800 D 3600 Answer : B Explanation :
8.
 Doppler shift principle is used in the measurement of A Temperature B Frequency C Speed D Pressure Answer : C Explanation :
9.
 The accelerometer using  LVDT  has the advantage of A High natural frequency B Being-contactless device C Better resolution D All of the above Answer : D Explanation :
10.
 The accelerometer used for measurement of vibration of large structures is A Servo-accelerometer B Piezoelectric accelerometer C Potentiometric accelerometer D Strain gauge accelerometer Answer : A Explanation :
11.
 The most common transducer for shock and vibration measurement is A Dial gauge B Ring-type load cell C LVDT D Piezoelectric pickup Answer : D Explanation :
12.
 The drawbacks of radiation pyrometers are that A Their initial as well as installation costa are high B They need maintenance C Each pyrometer needs individual calibration D All of the above Answer : D Explanation :
13.
 In optical pyrometers temperature is measured by A Thermocouple effect B Photocell principle C Comparison of brightness of the source with that of a standard source. D None of the above Answer : C Explanation :
14.
 Which of the following is the best method for measurement of temperature of hot bodies radiating energy in visible spectrum  ? A Thermocouple B Thermopile C Optical pyrometer D Bolometer Answer : C Explanation :
15.
 Which of the following is used to measure temperature inside a boiler furnace  ? A Resistance thermometer B Bimetallic thermometer C Optical pyrometer D Thermistor Answer : B Explanation :
16.
 Which is the most suitable thermocouple transducer for the measurement of temperature in the range of 1,000C  to  1,5000C  ? A Chromel-alumel B Platinum-rhodium C Iron-constantan D Chromel-constantan Answer : B Explanation :
17.
 Which of the following thermocouple pairs has maximum sensitivity around 273 K  ? A Nichrome-constantan B Copper-Nickel C Platinum-constantan D Nickel-constantan Answer : A Explanation :
18.
 Optical pyrometer is generally used to measure A Low pressure B Low temperature C High temperature D High pressure Answer : C Explanation :
19.
 A Reynold’s number of 1000 indicates A Turbulent flow B Laminar flow C Both Turbulent and Laminar flow D None of the above Answer : B Explanation :
20.
 The flow rate of electrically conducting liquid without any suspended particle cannot be measured by A Turbine flow meters B Electromagnetic flow meters C Ultrasonic flow meters D Thermistor based heat loss flow meters Answer : D Explanation :
21.
 A hot-wire anemometer is a device used to measure  : A Gas velocities B Pressure in gases C Liquid discharge D Temperature Answer : A Explanation :
22.
 The device used for measuring flow of air around an aeroplane is A Rotameter B Venturi meter C Anemometer D None of these Answer : C Explanation :
23.
 Which of the following flow meters is capable of giving the rate of flow as well as the total flow  ? A Nutating disc flow meter B Electromagnetic flow meter C Orifice meter D Lobed impeller flow meter Answer : B Explanation :
24.
 The main drawbacks of ultrasonic flow-meter are A Low accuracy and slow response B Complexity and relatively high cost C Affected by pressure and temperature variations D None of the above Answer : B Explanation :
25.
 Hydrometer is employed for determination of A Relative humidity B Specific gravity of liquids C Fluid level D None of the above Answer : B Explanation :
26.
 Inductive method can be used for measuring thickness of A Magnetic but non-conducting materials B Conducting but non-magnetic materials C Conducting and magnetic materials D Both magnetic and non-magnetic materials, as well as non-conducting and conducting materials Answer : D Explanation :
27.
 Which of the following transducers is most suitable for monitoring continuous variations in very fine thickness of a material  ? A Diaphragm B Capacitor C LVDT D Piezoelectric crystal Answer : B Explanation :
28.
 The electrical transducers used for continuous recording and control of humidity are A Resistive hygrometers B Electrolytic hygrometers C Aluminium oxide hygrometers D All of the above Answer : D Explanation :
29.
 Measurements of flow, thermal conductivity and liquid level using thermistros make use of A Resistance decrease with temperature B Resistance increase with temperature C Self-heating phenomenon D Change of resistivity Answer : A Explanation :
30.
 In viscosity meters the quantity measured is A Buoyant force B Frictional force C Coriolis force D Centrifugal force Answer : B Explanation :
31.
 The function of the reference electrode in a  pH  meter is to A Produce a constant voltage B Provide temperature compensation C Provide a constant current D Measure average  pH  value Answer : A Explanation :
32.
 The method used for analysis of gases and their mixtures is called as A Thermal conductivity B Electrical conductivity C Relative humidity D Specific gravity Answer : A Explanation :
33.
 The disadvantage(s) of capacitor microphones is/are A Higher cost B High voltage supply requirement C Limited frequency range D Both (a) and (b) Answer : C Explanation :
34.
 The devices extensively used in sound measurement system are A Capacitor microphones B Carbon microphones C Dynamic microphones D Vibration pickups Answer : D Explanation :
35.
 A linear displacement digital transducer uses A BCD code B Gray code C Hexadecimal code D Binary code Answer : B Explanation :
36.
 Which if the following moving particles cannot be deflected by magnetic fields  ? A $\alpha&space;-particles$ B Neutrons C Protons D Electrons Answer : B Explanation :
37.
 Geiger counter has the advantages of A Being relatively inexpensive, reliable and rugged in construction B Producing easily countable large pulses C Having response independent of variation in humidity, temperature and atmospheric pressure. D All of the above Answer : D Explanation :
38.
 Scintillation counters have the advantage(s) of A Very fast counting rate B Capability of detecting of radiations of lower levels C Capability of detecting of x-rays D All of the above Answer : D Explanation :
39.
 Analog data acquisition system are used when A Wide bandwidth and low accuracy are required/sufficient. B Narrow bandwidth and low accuracy are required/sufficient. C Wide  bandwidth and high accuracy are required. D Narrow bandwidth and high accuracy are required. Answer : A Explanation :
40.
 In AC bridge if the supply frequency is 1000 Hz, the detector will be A Ballistic galvanometer B D’ Arsnoval galvanometer C Vibration galvanometer D Telephone Answer : D Explanation :
41.
 _____________  bridge is used for the precise measurement of inductances over a wide range. A Hay’s B Wien’s C Anderson D Maxwell Answer : C Explanation :
42.
 Which of the following bridges is used to measure power factor? A Wien’s bridge B Maxwell bridge C Schering bridge D Kelvin bridge Answer : C Explanation :
43.
 Moving parts of instruments are supported in  ___________  bearings. A Jewelled B Ball C Roller D Bush Answer : A Explanation :
44.
 A power factor meter has  ____________  control springs. A One B Two C Four D No Answer : D Explanation :
45.
 Dead time of the instrument is A The time required by an instrument to begin to respond to a change in the measurand B The time required by an instrument for initial warming up C The largest change of input quantity for which there is no output of the instrument D None of the above Answer : B Explanation :
46.
 In resistance thermometers platinum is used because of A Low cost B Low cost and high stability C Low cost, high stability and wide operating range D None of the above Answer : C Explanation :
47.
 Changes in atmospheric temperature, humidity etc. cause  __________ errors. A Cumulative B Systematic C Environmental D Instrumental Answer : C Explanation :
48.
 In electrical measuring instruments, electrical energy is converted to A Mechanical energy B Heat energy C Chemical energy D Light energy Answer : A Explanation :
49.
 Megger is used to measure A Breakdown voltage of insulation B Earth resistance C Insulation resistance D None of above Answer : C Explanation :
50.
 Sensitivity of a voltmeter is given by the A Ohms per volt B Reciprocal of full scale deflection current C Both (a) and (b) D None of the above Answer : C Explanation :
51.
 Control springs are made up of A Phosphor bronze B Copper C Silver D Steel Answer : A Explanation :
52.
 In the case of indicating instruments the function of the control spring is A To apply controlling torque B To pass electric current to moving system C Both (a) and (b) D None of the above Answer : C Explanation :
53.
 Torque weight ratio will be least in ___________  instruments. A Dynamometer B Moving iron C Moving coil D All above Answer : A Explanation :
54.
 Megger is operated by A Internal battery B An external voltage source C An internal hand driven generator D None of the above Answer : C Explanation :
55.
 Megger will give resistance values which A Increase with the speed of the hand driven dynamo B Decrease with the speed of the hand driven dynamo C Remain constant irrespective of the speed D Any of the above Answer : C Explanation :
56.
 Primary of an instrument transformer (C.T.) is connected in A Series with the line B Parallel with the line C Across two lines D Any of the above Answer : A Explanation :
57.
 Vibrating reeds are used in which of the following instruments? A Power factor meter B Frequency meter C Wattmeter D Synchronoscope Answer : B Explanation :
58.
 If voltage supply to the energy meter is more than the rated value, energy meter will run A Slow B Fast C Either of the above D None of the above Answer : A Explanation :
59.
 Aluminium is selected as the material for rotating disc of energy meter because A It is good conductor B It is light C It is indigenously available D All of the above reasons Answer : D Explanation :
60.
 For making shunts the material suitable is that which has A Negligible thermoelectric e.m.f. with copper B Same resistance temperature co-efficient as the coil of the instrument C Been annealed properly so that its resistance does not change with time D All of the above properties Answer : D Explanation :
61.
 Meter ranges are so selected that the indications are obtained near the A Top of the scale B Bottom of the scale C Middle of the scale D None of the above Answer : C Explanation :
62.
 For measuring an unknown electrical quantity, select the meter with A Highest range and work down B Lowest range and work up C With middle range and work up and down on trial and error basis D Any of the above Answer : A Explanation :
63.
 Moving iron meters are extensively used for the measurement of AC voltage and current because A No current flows through the moving element and is robust B Its torque weight ratio is more C It is very accurate D All of the above Answer : A Explanation :
64.
 Moving iron instruments are rarely used in low power high resistance circuits because of A High resistance of the coil B Low reluctance of magnetic path C High reluctance of magnetic path D None of the above Answer : C Explanation :
65.
 Scale of an instrument will ne uniform if A Deflecting torque varies directly as the deflection angle B Control torque varies directly as the deflection angle C Both (a) and (b) D Damping torque varies directly as the deflection angle Answer : C Explanation :
66.
 Swamping resistance is used to A Compensate the error due to temperature variations B Compensate the error due to strong magnetic field C Both (a) and (b) D None of the above Answer : A Explanation :
67.
 Which of the following instruments may be used to measure DC voltage accurately? A Moving iron type instrument B Moving coil type instrument C Electrodynamic type instrument D None of the above Answer : B Explanation :
68.
 A high resistance is usually connected in series with an electrostatic voltmeter A To render the measurement accurate B To increase the range C For safety reasons D None of the above Answer : C Explanation :
69.
 A milli-ammeter can be used as A An ammeter only B A voltmeter C Both voltmeter and ammeter D None of the above Answer : C Explanation :
70.
 Weston cell is a A Good source of current B Good source of power C Good standard of voltage D None of the above Answer : C Explanation :
71.
 Deflection of a hot wire instrument is proportional to A Maximum value of alternating current B Instantaneous value of alternating current C RMS value of alternating current D Average value of alternating current Answer : C Explanation :
72.
 Following type of instrument is used to measure very small currents of high frequency A Induction type instrument B Dynamometer type instrument C Permanent magnet moving coil type ammeter D Thermocouple type instrument Answer : D Explanation :
73.
 In which part of the scale does the pointer indicate most accurately? A In the first third of the scale B In the first half of the scale C In about the middle of the scale D In the last third of the  scale Answer : D Explanation :
74.
 The accuracy of a meter is determined by  ____________  deflection. A One-tenth of full scale B One-fourth of full scale C Half-scale D Full-scale Answer : D Explanation :
75.
 The sensitivity inaccuracy of an instrument does not depend on A Frequency response B Hysteresis C Amplitude distortion D All of the above Answer : D Explanation :
76.
 The error, when reading at half-scale in an instrument, is A Equal to half of full-scale error B Equal to full-scale error C Less than full-scale error D Greater than full-scale error Answer : D Explanation :
77.
 An instrument’s reliability means A The extent to which the characteristics remain linear B The life of the instrument C The degree to which the repeatability continues to remain within specific limits D All of the above Answer : C Explanation :