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Tuesday 13 August 2013

Electrical online august

1.       In an N-Type Semiconductor, the majority current Carriers are _electrons_.
2.       . Which of the listed precautions should take while cleaning poly phase motor internals with compressed air? (Multiple ans)
A. Open the machine as both ends so as to allow the dust to escape
B. Be certain that the circuit breaker is opened ,tagged as the feeder panel
C. Be certain that air is clean and as dry as possible

D. Ensure that the fuse is removed
3.       . Which of the following statements represents an application of a silicon controlled rectifier?
A. To provide DC power for a main propulsion motor.
B. For use as a voltage reference diode.
C. For sensing flame in an automated burner.
D. To eliminate power supply hum.
4.       When paralleling an AC generator with live bus bars, which of the following precautions are applicable?
A. Generator frequency should be slightly lower than bus bar frequency
B. Generator frequency should be slightly higher than bus bar frequency
C. Generator voltage should be in phase with bus bar voltage
D. Generator voltage should be out of phase with bus bar voltage
5.       . If an intrinsic semiconductor is doped with a very small amount of boron then the extrinsic semiconductor set formed, the no. of electrons and holes will
A. Both decreases
B. Increase and decrease
C. Both increase
D. Decrease and increase
6.       . A poly phase motor driving an engine room pump fails to start, when trying to identify the cause of failure, which of the following steps are applicable.(multiple ans)
A. visually examine the motor for open circuit fault
B. visually examine the stator for open circuit fault

C. Reverse the direction of current for its working
D. Perform the infinite resistance test
7.       With reference to the data logger for a refrigerate sys. Which of the parameters should be noted?
A. sea water temp, pressure
B. condenser temp
C. Refrigerant leakage
D. Evaporator temp.
8.       . When the current through the coil of an electromagnet is reversed, the direction of magnetic field also reversed (TRUE or FALSE)
9.       . W.r.t to a data logger for a refrigerant sys. Which of the following parameters should be checked?
A. room temp
B. liquid ref temp

C. Recharge temp.
D. Solenoid valve operation
10.  *Open-loop transfer function of a system having one zero with positive real values is called nonminimum phase function
11.   Which of the listed devices may be installed on a large turbo-electric alternating
current propulsion generator?

A. Temperature detector coils inserted in the stator slots for measuring stator temperature.
B. A CO2 fire extinguishing system.
C. Electric space heaters to prevent condensation of moisture.
D. All of the above
12.   Which of the listed conditions is an advantage of a PN diode over a vacuum diode?
A.    Longer life.
B.    No warm up time.
C.    Less delicate.
D.All of the above
13.   Which of the following conditions will occur when solenoid coil burns out of a cargo winch with a electrical brake.
A.The brake will be set by spring force.
B.The motor will over speed and burns out
C.The load suspended by the cargo boom will fail
D.Nothing will happen, the winch will continue to operate normally
14.   Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly fluctuating temperatures, an ambient compensating element must be used. This element consists of a
A.Cylindrical spring on the contact arm.
B.Conical spring on the contact arm.
C.Second bimetal element.
D.Second electromagnet.
15.   Vgs and Id approximately zero....this is called cutoff voltage
16.   *A poly-phase motor driving an engine room pump fails to start. When trying to identify the cause of failure, which of the following steps are applicable?(Multi Ans)
A. Ensure that the isolator is open.
B. Make sure that there is no restriction preventing movement of pump/motor.
C. Check whether the overload relay has tripped.

D. Check whether battery is fully charged

17.   In a Transistor
A.PNP and NPN are two basic types
B.Emitter,Collector and Base are the basic Elements.
C.Collector separates Base and Emitter
D.Emitter separates Base and Collector

18.   The basic measuring unit of inductance is the
A.coulomb
B.ohm
C.farad
D.henry

19.A certain appliance uses 750 W. If it is allowed to run continuously for 15 days, how many kilowatt-hours of energy does it consume?
 
Variable
Answer
Units
Correct to
 KwH
270 
 KwH
 0 decimal
20.What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it?
 
Variable
Answer
Units
Correct to
 MMF
300 
 At
 0 decimal
21. A semiconductor is damaged by a strong current, because of (1)________ (2)________ (3)________


1) SHORT CIRCUIT

2) OVERLOAD

3) OVERCURRENT
SOME OTHER Q WHRE ANS WAS ZENER AND AVALANCHE EFFECT AND REVERSE BAIS BREAKDOWN

22. which of the following capacitor is having highest di electric constant
A.air gap
B.glass
C. paper
D.polyster
23. the conductive loop of the rotor of a simple two poles,single phase generator rotates at 400 rps.cal the frequency induced output voltage
ANS  400HZ
SAME Q WITH 1200 RPS ANS 1200 HZ
24.SOME Q IN WHICH THERE R 4 CAPACITORS 6,8,3,10 IN SERIES. FIND THEIR EFFECTIVE
ANS 1.37 FARAD
25. A certain appliance use 350W, if it is allowed to run continous for 24 days , how many kw of energy does it consume (fill in the blank)
ans 201.6 kwhr

26. Alfa particles enter an electromagnetic field where the electric intensity is 600v/m and the magnetic induction is 0.200T what is the velocity of alfa particles?
ANS 2000 M/S

27. What happens to the strength of electro magnetic field when current passing through an inductor is halfed ________
a. ¼
b. ½
c. 2
d. 4

28. Find the amps required by the electrical bulb,if the elecrtonmakes ??10?? moves about 22 elecrtons in one hour.assume a charge at electron be -1.602*10^19.
ANS .445
IN EXAM IT WAS ASKED FOR 0.25 HOUR…




29.which of the following states concerning Analog and digital devices is correct
a.the variable in digital are fixed & in analog they are continuous qtys.
b.no basic diff between the 2
c.analog devices r superior in accuracy as comp to digital.
d.operations in digi device r performed simultaneously.

30.reverse current prevents dc gen motoring by
a.redirecting the load
b.speeding up the prime mover
c.securing the excitor generator
d.tripping the crkt breaker.

31.some q abt varnished cambric
Ans cotton cloth with insulated varnish

32.in an ac synchronous motor electric prop plant, propeller speed is cont varied by:
a.prime mover speed.
b.elec coupled field strength
c.no of energizing main motor poles
d.propulsion gen field strength.


Good luck………………!!!

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