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MCQ
4341. 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.
4342. 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,
4343. 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.
4344. 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°
4345. 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.
4346. 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
4347. 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.
4348. 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.
4349. 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.
4350. A 1000V power supply would use as a filter capacitor-
paper capacitor
mica capacitor
electrolytic capacitor
air capacitor
4351. 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.
4352. In order to achieve high accuracy, the slide wire of a potentiometer should be-
As long as possible
As short as possible
Neither too small nor too large
Very thick
4353. The internal resistance of an ammeter should be-
Very small
High
Medium
Infinity
4354. 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.
4355. Direct method is used to measure-
Length
Pressure
Temperature
Voltage
ব্যাখ্যা: Direct method is used to measure length.
4356. 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.
4357. In a moving coil instrument, the deflecting torque is proportional to-
Current
Square of the current
Squareroot of the current
Sine of the measurand
ব্যাখ্যা: একটি ইনস্ট্রুমেন্টের ডিফ্লেকটিং টর্ক (To), যে কারেন্ট (1) পরিমাণ করতে হবে তার সাথে সরাসরি সমানুপাতিক।
4358. 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
4359. 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.
4360. 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.