14 August 2016

ELCTRIAL QUESTIONS AND ANSWERS-MCQ-6-ETO


QUESTIONS AND ANSWERS FOR ETO

1.Which of the following statements concerning the maintenance of solid-silver contacts in relays and auxiliary control circuits is correct?               
A. When necessary, they should always be dressed with a wire wheel.            
B. They should be filed with a fine-cut file when projections extend beyond the contact surface.             
C. When black silver oxide is present, it should always be  removed from the contact surface with coarse sandpaper.     
D. If necessary, they should be held together with moderate pressure while emery paper is drawn between the contacts.           
Ans : B

2. While starting a main propulsion synchronous motor, the  ammeter pegs out at maximum and then returns to the proper value after synchronization. This indicates the   _____________. 
A. motor has started properly       
B. field windings are grounded      
C. slip rings are dirty        
D. power transmission cables are grounded             
Ans : A  

3. The purpose of a short circuit forcing module (short time trip) installed in a branch line is to provide ____________.   
A. high speed clearance of low impedance short circuits in the branch             
B. continuity of service on main bus under short circuit  conditions in a branch              
C. isolation of short circuits by selective tripping of branch circuit breakers    
D. all of the above             
Ans : D  

4. Which of the following electric motors would be the safestand most reliable to use on the main deck of a vesselin foul weather conditions?         
A. Sealed motors               
B. Drip proof motors        
C. Enclosed motors           
D. Watertight motors      
Ans : D

5. A direct current passing through a wire coiled around a soft iron core is the description of a simple ____________.    
A. magnetic shield            
B. electromagnet              
C. piezoelectric device     
D. electromagnetic domain            
Ans : B

6. To properly use a hook-on-type volt/ammeter to check  current flow, you must FIRST _____________.            
A. de-energize the circuit to allow connection of the   instrument in series     
B. hook the jaws of the instrument around the insulated  conductor 
C. connect the voltage test leads to the appropriate terminals          
D. short the test leads and calibrate the instrument to zero
Ans : B 
 
7. The use of four diodes, in a full-wave bridge rectifier  circuit, will __________.         
A. provide unidirectional current to the load             
B. allow a very high leakage current from the load  
C. convert direct current to alternating current       
D. offer high opposition to current in two directions               
Ans : A

8. Autotransformer starters or compensators are sometimes usedwith polyphase induction motors to _____________.               
A. reduce the voltage applied to the motor during the starting period              
B. increase the voltage for "across-the-line starting"            
C. provide a backup means of voltage regulation for emergency starting        
D. allow the voltage to be either stepped up or down, depending on the application, to ensure full torque
Ans : A

9. A molded-case breaker provides protection against short  circuits by using a/an ____________.
A. shading coil    
B. arc quencher 
C. electromagnet              
D. holding coil     
Ans : C  

10. When troubleshooting electronic equipment, you should use ahigh impedance multimeter ________________.        
A. to prevent excess current flow through the meter that would damage it   
B. for AC measurements only and a low resistance meter for DC measurements         
C. whenever a low impedance meter is not available, regardless of the components being tested          
D. so as not to load down the circuit and obtain erroneous  voltage readings 
Ans : D

11. Which of the listed devices is used to measure pressure andconvert it to an electrical signal?
A. Transducer     
B. Reducer          
C. Transformer  
D. Rectifier          
Ans : A

12. Grounds occurring in electrical machinery as a result of insulation failure may result from _____________. 
A. deterioration through extended use       
B. excessive heat              
C. extended periods of vibration   
D. all of the above
Ans : D

13. The amount of voltage induced in the windings of an AC  generator depends on ____________.      
A. the number of conductors in series per winding  
B. the speed at which the magnetic field passes across the  winding
C. the strength of the magnetic field           
D. all of the above             
Ans : D

14. A motor using a rheostat in the motor circuit to vary the speed is called a ____________. 
A. squirrel-cage induction motor  
B. regenerative braking motor      
C. wound-rotor induction motor   
D. synchronous motor     
Ans : C

15. When reading electrical motor controller diagrams, it helps to know that ____________.
A. current paths in the control circuit are drawn as heavy  lines and in the power circuit as lighter lines
B. current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines        
C. circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter lines
D. circuits subject to 500 volts or greater are drawn as light lines and below 500 volts as heavy lines
Ans : B  

16. Which of the following precautions should be taken when  troubleshooting various power circuits using a common solenoid-type mechanical voltage tester (wiggins)?          
A. Never use this tester on circuits greater than 60 Hz, as the coil's resultant high impedance lowers current and magnetic pull. The tester may not register dangerous voltages.            
B. Always remember that the unit is polarity sensitive and if used on DC circuits reversing the leads may result in high temperatures within the tester.              
C. Never connect the device to circuits where potentials  greater than 120 volts may be present, as the coil's  extremely fine wire cannot withstand more than a few amps. 
D. Always pre-set the meter to the next higher range than the amount of voltage expected in the circuit in order to  prevent damage from an off-scale reading.               
Ans : A  

17. The device that most commonly utilizes the principle of  electromagnetic induction is the _____________. 
A. diode
B. transformer   
C. transistor       
D. rheostat         
Ans : B 
 
18. A tubular fuse should always be removed from a fuse panel with _____________.               
A. a screwdriver
B. a pair of insulated metal pliers 
C. any insulated object    
D. fuse pullers    
Ans : D 

19. One factor that determines the frequency of an alternator is the ____________. 
A. number of turns of wire in the armature coil        
B. number of magnetic poles         
C. strength of the magnets used  
D. output voltage              
Ans : B

20. The variable resistance placed in the rotor circuit of a wound-rotor induction motor provides for __________.           
A. speed control
B. frequency control         
C. voltage control              
D. use as a split-phase motor        
Ans : A

21. Which of the motors for the devices listed below is fitted with an instantaneous overload relay?     
A. Fan   
B. Pump               
C. Winch              
D. Machine tool 
Ans : C  

22. A molded-case circuit breaker provides protection against short circuits by using a/an ________________.
A. electromagnet              
B. shading coil    
C. arc quencher 
D. burn away strip            
Ans : A  

23. Which of the following statements concerning analog anddigital devices are correct?         
A. The variables in digital systems are fixed quantities, and the variables in analog systems are continuous quantities.  
B. There are no basic differences between the two systems.              
C. Analog devices are superior in accuracy compared to digital devices.          
D. Operations in a digital device are performed simultaneously.        
Ans : A 
 
24. The number of cells in a 12 volt lead-acid battery is  ________________.
A. three cells      
B. four cells         
C. six cells            
D. twelve cells    
Ans : C

25. The Wheatstone bridge is a precision measuring instrument utilizing the principle of changes in _____________.     
A. inductance     
B. capacitance   
C. resistance      
D. amperage      

Ans : C


 "Things work out best for those who make the best of how things work out." --John Wooden

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ELCTRIAL QUESTIONS AND ANSWERS-MCQ-6-ETO
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