EC
Engineering Classroom
by Himalay Sen

Exams

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Board Questions

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MCQ
4541. ACSR means-
Aluminium core steel reinforced
Aluminium conductor steel reinforced
Aluminium copper steel reinforced
reinforced all conductor steel
ব্যাখ্যা: ব‍্যাখ্যা: ACSR = Aluminium conductor steel reinforced.
4543. Advantages of higher trans mission voltage is/are--
Power transfer capability of the transmission line is increased
Transmission line losses are reduced
Area of cross section and volume of the conductor is reduced
all of the above
4545. The presence of earth in case of overhead lines-
increase inductance
increase capacitance
decrease inducatance
decrease capacitance
ব্যাখ্যা: ব‍্যাখ্যা: As the earth is considered to be an infinite source of electrons, the presence of overhead lines causes charge currier to be separated by a dielectric (air), causing an increase in capacitance.
4546. The skin effect shows that-
the distribution of AC current is uniform through the cross section of the conductor
current density is more at the centre of the condutor
current density is lower at the surface of the condutor
current density is more at the surface of the condutor
ব্যাখ্যা: ব‍্যাখ্যা: The skin effect depends on the surface area of the conductor. The skin effect in the solid conductor is more than the stranded conductor because the solid conductor has more surface area.
4548. Which of the following rotor is used in thermal power plants?
cylindrical rotor
salient pole rotor
squirrel cage rotor
either of these
ব্যাখ্যা: ব্যাখ্যা: Cylindrical rotor is also called as round rotor or smooth rotor. This rotor is mechanically very strong It's used in thermal power plants.
4552. If the frequency is increased, then skin effect will—
increases
decreases
remains unaffected
any of the above
ব্যাখ্যা: ব‍্যাখ্যা: The skin effect increases with the increase frequency
4554. When power is to be transmitted over a distance of 250km, the transmission voltage should be-
66kV
132kV
33kV
11kV
ব্যাখ্যা: Transmission lines are three types-Short transmission line (A length less than 80 km (50 miles) and voltage level less than 69kV) Medium Transmission line (A length more than 80km (50 miles) but less than 250km (150 miles) and voltage level is from 69kV to 132kV) Long transmission line (A length more than 250 km (150 miles) and voltage level is above 132kV)
4559. Suspension insulators are used when transmission voltage is-
high
low
fluctuating
steady
ব্যাখ্যা: ব্যাখ্যা: When transmission voltage is greater than 33kV, thes suspension insulator is used. It is consist of a number of glass or porcelain dises connected in series by metal links in the form of a string.
4560. Proximity effect is more in case of-
power cables
same in both cases
overhead lines
none of the above
ব্যাখ্যা: ব‍্যাখ্যা: Proximity effect is more in case of power cables. because the distance between the conductor is small.