Question Paper: Electronics and Electrical Engineering : Question Paper Dec 2014 - Mechanical Engineering (Semester 4) | Pune University (PU)
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## Electronics and Electrical Engineering - Dec 2014

### Mechanical Engg (Semester 4)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.

### Solve any one question from Q1 and Q2

1 (a) Draw and explain the architectural block diagram of 8051 microcontroller.(6 marks) 1 (b) What is Timer/Counter Control (TCON) register ? Explain the significance of various bits in it.(6 marks) 2 (a) What is meant by baud rate ? Differentiate between serial and parallel data transfer schemes.(6 marks) 2 (b) Explain different addressing modes supported by 8051 Microcontroller.(6 marks)

### Solve any one question from Q3 and Q4

3 (a) State the expression for torque developed in a three-phase induction motor. Hence obtain:
(i) condition for maximum torque and
(ii) expression for maximum torque.
(6 marks)
3 (b) Why is a starter required for d.c. motor ? Discuss the working of three-point starter with the help of neat Schematic.(7 marks) 4 (a) Distinguish between squirrel cage and slip ring induction Motors.(6 marks) 4 (b) A 230 V, 4 pole, lap wound d.c. shunt motor takes no-load current of 4 A when running at 1200 rpm. The resistance of armature winding is 0.1 Ω and shunt field winding is 115 Ω. Total brush contact drop is 2 V. If it takes current of 60 A on full load, calculate its full load speed. Assume that flux gets weakened by 5% on full load condition due to armature reaction.(7 marks)

### Solve any one question from Q5 and Q6

5 (a) Draw the block diagram showing basic structure of CRO and explain the function of various components.(6 marks) 5 (b) Explain the working of audio signal generator with the help of block diagram.(6 marks) 6 (a) Explain the working of digital multimeter with the help of block diagram.(6 marks) 6 (b) Compare analog and digital voltmeters.(6 marks)

### Solve any one question from Q7 and Q8

7 (a) Explain single wattmeter method for measuring three-phase reactive power in delta connected balanced load with the help of neat circuit diagram and phasor diagram.(6 marks) 7 (b) What is an A.C. bridge ? Enlist A.C. bridges. Derive the general equations for balance of an A.C. bridge.(7 marks) 8 (a) State advantages and disadvantages of electrostatic instruments.(6 marks) 8 (b) A 3-phase, 400 V, 50 Hz a.c. motor is working on certain load having 0.5 lag power factor. Two wattmeters are connected to measure input power of the motor which show total power of 40 kW. Find reading of each wattmeter and total reactive power of motor.(7 marks)