**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 Theveninâ€™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