This Portion of Electrical andElectronic Measurements and Measuring instruments contains Analog Instruments MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.
This Section covers below lists of topics.
- Analog Instruments.
- Classification of Analog Instruments.
- Principles of Operation.
ELECTROMECHANICAL INDICATING INSTRUMENTS
- Operating forces.
- Constructional Details.
- Types of Supports.
- Torque/Weight Ratio.
- Control Systems.
- Damping System
- Permanent Magnets.
- Pointers and Scales.
- Recording Instruments.
- Integrating Instruments.
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. If an analog PMMC 0 – 10 A ammeter is provided with no controlling mechanism and the moving part are free to rotate, what will be the reading of the instrument if a current of 1 A (d.c) passed through the moving coil (the torque produced is sufficient to overcome the frictional losses)
- 1 A
- 10A
- The pointer will continuously rotate
- The pointer will remain stationary.
C. The pointer will continuously rotate
2. A spring controlled instrument uses phosphor bronze springs to produce controlling torque. if the ratio of length of spring to thickness of spring is 3000 for a deflection 90°, what should be this ration if the scale is to extended to 120°
- 4000
- 2250
- 2000
- None of the above.
A. 4000
3. A voltage of 200 V produce a deflection of 90° in a PMMC spring controlled instrument. if the same instrument is provided with gravity control, what would be the deflection?
- 90°
- 45°
- 64.2°
- Cannot be not from the data given
D. Cannot be not from the data given
4. A spring produces a controlling torque of 16 × 10-6 Nm for a deflection of 120°. Suppose its width and length are made two times their original value and thickness is halved , the value of controlling torque for the same deflection will be :
- 16 × 10-6 Nm
- 8 × 10-6 Nm
- 32 × 10-6 Nm
- 2 × 10-6 Nm
D. 2 × 10-6 Nm
5. Air friction damping should not be used where the deflecting torque in the instrument is produced due to
- Magnetic field
- Electrostatic field
- Thermo-electric emf
- None of the above.
D. None of the above.
6. Fluid friction damping can be used in
- Horizontally mounted instruments
- Vertically mounted instruments
- Both in horizontally and vertically mounted instruments
- None of the above
B. Vertically mounted instruments
7. Permanent magnets used in the instruments are hard core materials because
- They have broad hysteresis loop
- Their energy density is high
- They have a high (BH)max produced
- All of the above.
D. All of the above.
8. A spring produces a controlling torque of 16x10-6 Nm for a deflection of 120Y. If the width and length become two times their original values and the thickness is halved, the value of controlling torque for the same deflection will be
- 16 × 10-6 N
- 8x10-6 Nm
- 2x10-6 Nm
- 32x10-6 Nm
C. 2x10-6 Nm
9. The shunt resistance in an ammeter is usually
- less than meter resistance
- equal to meter resistance
- more than meter resistance
- of any value
A. less than meter resistance
10. A voltage of 200 V produces a deflection of 90° in a PMMC spring-controlled instrument. If the same instrument is provided with gravity control, what would be the deflection?
- 45°
- 65°
- 90°
- cannot be determined by the given data
C. 90°
11. The high torque to weight ratio in an analog indicating instrument indicates
- high friction loss
- nothing as regards friction loss
- low friction loss
- none of the above
C. low friction loss
12. Swamping resistance is connected
- in series with the shunt to reduce temperature error in shunted ammeter
- in series with the ammeters to reduce errors on account of friction
- in series with meter and have a high resistance temperature coefficient in order to reduce temperature errors in ammeters.
- in series with the meter and have a negligible resistance co-efficient in order to reduce temperature errors in shunted ammeters
D. in series with the meter and have a negligible resistance co-efficient in order to reduce temperature errors in shunted ammeters
13. Moving-iron instruments when measuring voltages or currents
- indicate the same values of the measurement for both ascending and descending values
- indicate higher value of measurand for ascending values
- indicate higher value of measurand for descending values
- none of the above
C. indicate higher value of measurand for descending values
14. A moving-iron type of instrument can be used as
- standard instruments for calibration of other instruments
- transfer-type instruments
- indicator-type instruments as on panels
- all of the above
C. indicator-type instruments as on panels
15. In spring-controlled moving iron instruments, the scale is
- uniform
- cramped at the lower end and expanded at the upper end
- expanded at the lower end and cramped at the upper end
- cramped both at the lower and the upper ends
B. cramped at the lower end and expanded at the upper end
16. Thermocouple instruments can be used for a frequency range
- up to 500 Hz
- up to 5 MHz
- up to 100 Hz
- up to 1 MHz
D. up to 1 MHz
17. The reason why eddy-current damping cannot he used in a moving-iron instrument, is
- they have a strong operating magnetic field
- they are not normally used in vertical position
- they need a large damping force which can only he provided by air friction
- they have a very weak operating magnetic field and introduction of a permanent magnet required for eddy current damping would distort the operating magnetic field
D. they have a very weak operating magnetic field and introduction of a permanent magnet required for eddy current damping would distort the operating magnetic field
18. An electrodynamometer type of instrument finds its major use as
- standard instrument only
- both as standard and transfer instrument
- transfer instrument only
- indicator-type instrument
B. both as standard and transfer instrument
19. The frequency range of moving-iron instruments is
- audio-frequency band 20 Hz to 20 kHz
- very low-frequency band 10 Hz to 30 kHz
- low-frequency band 30 Hz to 300 kHz
- power frequencies 0 to 125 Hz.
D. power frequencies 0 to 125 Hz.
20. A voltage of 200 V at 5 Hz is applied to an electrodynamometer type of instrument which is spring controlled. The indication on the instruments is
- 200 V
- 0 V
- the instrument follows the variations in voltage and does not give a steady response
- none of the above
C. the instrument follows the variations in voltage and does not give a steady response
21. Spring-controlled moving-iron instruments exhibit a square law response resulting in a non-linear scale. The shape of the scale can be made almost linear by
- keeping rate of change of inductance, L, with deflection, θ, as constant
- keeping 1/∅ dL/(d∅) as constant
- keeping ∅ dL/(d∅)as constant
- keeping 1/(k∅) as constant, where k is the spring constant
C. keeping ∅ dL/(d∅)as constant
22. Electrostatic-type instruments are primarily used as
- ammeters
- voltmeters
- wattmeters
- ohmmeters
B. voltmeters
23. The sensitivity of a PMMC instrument is 10CkZ/V. If this instrument is used in a rectifier-type voltmeter with half wave rectification. What would be the sensitivity?
- 10 kΩ/V
- 4.5 kΩ/V
- 9 kΩ/V
- 22.2 kΩ/V
B. 4.5 kΩ/V
24. The heater wire of thermocouple instrument is made very thin in order
- to have a high value of resistance
- to reduce skin effects at high frequencies
- to reduce the weight of the instrument
- to decrease the over-ranging capacity of the instrument
B. to reduce skin effects at high frequencies
25. Which instrument has the highest frequency range with accuracy within reasonable limits?
- PMMC
- Moving iron
- Electrodynamometer
- Rectifier
D. Rectifier
26. Which meter has the highest accuracy in the prescribed limit of frequency range?
- PMMC
- Moving iron
- Electrodynamometer
- Rectifier
A. PMMC
