Download Model question papers & previous years question papers
|
Posted By: Mala Member Level: Diamond Posted Date: 14 Jan 2008
|
2005 Bangalore University Electrical and Electronics First/Second Semester B.E. Degree Examination, February/March 2005 Question paper
|
|
|
First/Second Semester B.E. Degree Examination, February/March 2005
Common to all branches.
(New Scheme)
Basic Electrical Engineering
Time: 3 Hrs.] [Max. Marks: 100
Note: Answer any FIVE full questions.
1. (a) Explain Fleming’s rules as applied to Induced emf’s (5 Marks)
(b) Define:
i) Self Inductance and
ii) Mutual inductance and obtain the relationship between these two. (8 Marks)
(c) Define RMS and average value of a sinusoidally varying current and find their values in terms of its peak value. (7 Marks)
2. (a) Show that the average power in a pure capacitive circuit with a sinusoidal voltage is zero. (6 Marks)
(b) A coil of power factor 0.6 is in series with a 100µf Capacitor. When connected to a 50Hz supply, the potential difference across the coil is equal to the potential difference across the capacitor. Find the resistance and inductance of the coil. (9 Marks)
(c) Two impedances (150 + j157) O are connected in parallel across a 220V, 50H = supply. Find the total current and power factor. (5 Marks)
3. (a) Derive the relationship between the line and phase quantities of a balanced star connected lead. (6 Marks)
(b) Three 100 O resistors are connected in i) Star & ii) Delta across a 415V. 50Hz, 3-phase supply. Calculate the line and phase currents and the power consumed in each case. (6 Marks)
(c) Estimate the power factor in each of the following cases of two Wattmeter method of measuring three phase power:
i) Wattmeter readings are equal
ii) Wattmeter readings are equal and opposite.
iii) Wattmeter reading are in the ratio 1:2
iv) One wattmeter reads zero. (6 Marks)
4. (a) Explain the following:
i) Armature winding of a DC machine
ii) Commutator of a DC machine
iii) Brushes of a DC machine (6 Marks)
(b) Explain the significance of back emf in de motors. (4 Marks)
(c) A 4-pole 250V series motor has wave connected armature with 1254 conductors. The flux per pole is 22wb. When the motor is taking 50A. The armature and series field coil resistances are respectively 0.3 O and 0.2 O. Calculate the speed and torque of the motor and also the power developed in watts.
(10 Marks)
5. (a) Draw the typical speed/load characteristics of i) shunt and ii) Series motors and draw the comments on their shapes ad mention the applications of these motors. (10 Marks)
(b) Explain the need of starter for DC motors. (5 Marks)
(c) A series motor should never be started without a load on it. Justify this statement. (5 Marks)
6. (a) What are the losses in a transformer? On what factors do they depend? And how are they minimised? (6 Marks)
(b) A single phase transformer has 400 primary and 1000 secondary turns. The net cross sectional area of the core is 60 cm2 . The supply is 500V. 50Hz. Calculate:
i) The peak value of flux density
ii) Voltage induced in the secondary and
iii) The number of secondary turns to induce a voltage of 2500V (6 Marks)
(c) Derive an expression of or the terminal voltage on no load of a star connected three phase alternator. (6 Marks)
7. (a) Explain how torque is produced in a three phase induction motor (6 Marks)
(b) A three phase 10 pole induction motor is supplied by a 6-pole alternator running at 1200 rpm. Calculate the speed of the motor for a slip of 3 percent. (6 Marks)
(c) Find the number of armature conductors in series per phase of a three phase. 50Hz, 10 pole alternator having 90 slots. The winding is to be star connected to give a line voltage of 11kV. When the flux is 160 mwb. The winding factor is unity. Also find the voltage regulation when the full load terminal voltage is 10.60 KV. (8 Marks)
8. (a) With a neat sketch explain the construction and working of a single phase energy meter. (8 Marks)
(b) Explain the different types of wiring used in practice. (6 Marks)
(c) Explain the brief:
i) fuses
ii) Specification of wires
iii) Earthing and its necessity. (6 Marks)
Return to question paper search
|
|
|
Submit Previous Years University Question Papers and
make money from adsense revenue sharing program
Are you preparing for a university examination? Download model question papers
and practise before you write the exam.