## 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 :