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CBSE Electrical Engineering Theory Question Paper Class 12th (2010)

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Series OSS                                                                                                                          Code No. 117

                                                                      ELECTRICAL ENGINEERING
                                                                                  (Theory)

Time allowed : 3 hours                                                                                          Maximum Marks : 60

Instructions :   Attempt all questions.

1. (a) Explain with diagrams what do you understand by:    3
(i)      in phase
(ii)     lagging
(iii)    leading
as applied to sinusoidal quantities.
(b) A coil when connected to D.C. supply of 100 volt takes 10 Ampere. When it is connected to A.C. supply of 100 Volt, 50 Hz it takes 5 Ampere. Calculate Resistance and Inductance of the coil.    4


                                              OR
(a) State Thevenin’s theorem and explain it with the help of simple network.    5
(b) What is resonance ?    2

 

 

2. (a) Explain the significance of power factor in an A.C. circuit.    3
    (b) Calculate the value of load resistance RL for maximum power transformation in the circuit shown below. Also calculate the value of maximum power.    2+2

                                      

 


3. What are the methods of measurement of power in a 3-phase system ? Explain two wattmeter method.

 


4. (a) Deduce the e.m.f. equation of a transformer.
    (b) Write  merits and demerits of ordinary transformer and auto-transformer.

 


5. What is the principle of generation and motoring ? Explain with block diagrams.

 


6. Explain with neat sketches the functions of each part of a D.C. machine.  Write the relationship between terminal voltage and induced e.m.f. for motoring and generating action.    6+4

 


7. (a) Name various types of 1-phase motors.    3
    (b) Explain the construction and principle of shaded pole motor.    7

 


8. What are the advantages and disadvantages of 3-phase induction motors over 1-phase induction motors ?    4





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