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MCQ
2981. Digital instruments are those which-
have numerical read out
use LED or LCD displays
have a circuitry of digital design
none of the above
ব্যাখ্যা: The instrument which represents the measured value in the form of the digital number (numaric number) is known is digital instruments.
2982. An oscilloscope indicates-
Peak to peak value of voltage
DC value of voltage
RMS value
Average value
ব্যাখ্যা: The automatic measurement of various parameters of the signal, like its frequency, peak-to-peak voltage, duty cycle and rise time.
2983. Alternating current is measured by-
Induction ammeter
Permanent magnet type ammeter
Electrostatic ammeter
Moving iron repulsion type voltmeter
ব্যাখ্যা: Alternating current is measured by induction ammeter because the operation of induction type instruments depends on the production of torque due to the reaction between two magnetic fluses having some phase difference between the flux of an AC magnet and the eddy current induced by this flux.
2984. In an energy meter braking torque is produced to--
Safeguard it against creep
Brake the instrument
Bring energy meter to stand still
Maintain steady speed and equal to driving torque
ব্যাখ্যা: In an energy meter, a barking torque is produced to maintain a steady speed and equal to driving torque. A permanent magnet positioned near the edge of the aluminum disc from the braking system.
2985. Ampere is one of the-
Supplementary units
Derived units
Base units
Units used to measure charge
ব্যাখ্যা: Current unit is Ampere. Ampere is SI base unit.
2986. The electrical power to a Meggar is provided by-
Battery
Permanent magnet DC generator
AC generator
Any of the above
ব্যাখ্যা: Megger is a Portable instrument to measure high insulation resistances. Ii basically works on the principle of electromagnetic induction. The electrical power to a meggar is provided by permanent magnet D.C generator.
2987. A current transformer has a single-turn primary and a 200-turn secondary and is used to measure a.c. current with the help of a standard 5A a.c. ammeter. This arrangement can measure a line current of up to amperes.
1000
5000
200
40
2988. In a Weston synchronoscope, the fixed coils are connected across-
Bus-bars
A lamp
Incoming alternator
None of the above
ব্যাখ্যা: in a western synchronoscope, the fixed coils are connected across incoming alternator.
2989. To avoid the effect of stray magnetic field in A.C. bridges we can use --
Magnetic screening
Wagner earthing device
Wave filters
Any of the above
ব্যাখ্যা: To avoid the effect of stray magnetic field in A.C bridges we can use magnetic screening or magnetic shielding. Magnetic screening is a technique used to prevent magnetization of metals nearby a magnet or current carrying conductor which is a source of magnetic field.
2990. The internal resistance of an ammeter should be-
Very small
High
Medium
Infinity
2991. The megger (Megaohmmeter) is exclusively designed for measuring-
Very high resistance
Very low resistance
Ground fault in power lines
Overload on DC motor
ব‍্যাখ্যা: The megger instrument for measuring the insulation resistance of electrical device was introduced by the British firm of Evershed and Vignoles in 1905. It can measure very high resistance like hundreds of megaohoms range
2992. A moving iron instrument can be used for-
DC only
AC only
Both DC and AC
None of the above
ব্যাখ্যা: মুভিং আয়রন ইনস্ট্রমেন্ট এসি ও ডিসি উভয় সরবরাহে ব্যবহৃত হয়।
2993. The pointer of an indicating instrument should be--
Very light
Very heavy
Either (a) or (b)
Neither (a) nor (b)
ব্যাখ্যা: The pointer of an indicating instrument should be very light
2994. For measurement of inductance having high value, we should use-
Maxwell's bridge
Maxwell Wien bridge
Hay's bridge
Any of the above
ব্যাখ্যা: The Hay's bridge is used for determining the self- inductance of the circuit. The bridge is the advanced from of maxwell's bridge. The maxwell's bridge is only appropriate for measuring the medium quality factor. For measuring the high quality factor the Hay's bridge is used in the circuit
2995. A 1000V power supply would use as a filter capacitor-
paper capacitor
mica capacitor
electrolytic capacitor
air capacitor
2996. The operating voltage of a Meggar is about-
6V
12V
40V
100V
ব্যাখ্যা: আমাদের দেশে সাধারণতঃ 500V, 1000V, 2000V-এর মেগার পাওয়া যায়। টেস্ট ভোল্টেজ অনুযায়ী মেগার ইনসুলেশন 'টেস্টার' বিভিন্ন প্রকারের হয়ে থাকে। যথা- 100V, 250V, 500V, 1000V, 2500V, 10,000V.
2997. The disc of an instrument using eddy current damping should be of-
Conducting and magnetic material
Non-conducting and magnetic material
Conducting and nonmagnetic material
None of the above
ব্যাখ্যা: Eddy current damping uses conducting and nonmagnetic material.
2998. Ryall crest voltmeter is used for measurement of--
AC voltage of any form
Low-frequency voltage
High-DC voltage
High-AC voltage
ব্যাখ্যা: High AC voltage measurement used Ryall crest voltmeter,
2999. Commonly used instruments in power system measurement are-
Induction
Rectifier
Moving coil or iron
Electrostatic
ব্যাখ্যা: Induction type instruments are commonly used in power system measurement. These types of instruments are used only for AC measurements.
3000. In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at----
0°
60°
90°
120°
ব্যাখ্যা: ডায়ানামোমিটার টাইপ পাওয়ার ফ্যাক্টর মিটারে দুটি প্রেসার কয়েলের প্ল্যানের মধ্যবর্তী কোণ 90° এবং 3- power factor meter প্রেসার সার্কিটদ্বয়ের মধ্যবর্তী কোণ 120°