MCQs Electrical Engineering

1.  The least expensive protection for over current in LV system is
(1) Isolator       
(2) Oil circuit breaker 
(3) Rewireble fuse   
(4) Air break CB                 
Ans  (3)
2.  Which of the following is used in liquid fuses ?
(1) Transformer oil         
(2) Sulphur hexafluoride 
(3)Distilled water       
(4)  Carbon tetrachloride
Ans  (4)
3.  The rating of a fuse wire is always expressed in
(1) amperes-hours       
(2) kWh  
(3) amperes         
(4) amperes - volts           
Ans  (3)
4. For protection of a very long extra high voltage line, which relay is used ?
(1)  Impedance relay     
(2) Mho type distance relay
(3) Percentage differential relay  
(4) Reactance type relay           
Ans (2)
5. HRC fuse provided best protection against -
(1) open circuit   
(2) overload  
(3)  reverse current
(4) short circuit       
Ans  (4)
6. The recovery voltage that appears across the circuit breaker contacts will be maximum for power factor of
(1)zero           
(2) 0.5
(3) 0.707              
(4) unity
Ans  (1)
7. An air blast circuit breaker is usually employed for :
(1) Instantaneous voltage   
(2) intermittent duty  
(3) repeated duty       
(4) short duty 
Ans  (3)
8. The making current of 3-phase breaker with rating 2000 MVA, 33 kV will be -
(1) 35 A          
(2) 50A
(3) 70 kA        
(4) 89 A.          
Ans  (4)
9. A circuit breaker is rated as follows : 1500 A, 33KV, 3 sec, 3- phase oil circuit breaker. Determine the making current ?
(1) 110  A          
(2 ) 35 A
(3) 1.5  A          
(4) 89 A                  
Ans  (4)
10.  If in a circuit breaker, the length of an are increases, then the are resistance-
(1) increases
(2) remains unchanged 
(3) become zero 
(4) decreases
Ans  (1)
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