R09 - December, 2011 - Regular Examinations - Set - 2.

II B.Tech I Semester Examinations,December 2011
BASIC ELECTRICAL ENGINEERING
Common to Information Technology, Computer Science And Engineering
Time: 3 hours Max Marks: 75
Answer any FIVE Questions
All Questions carry equal marks
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1. (a) A circuit consists of resistance R, and capacitive reactance of 60 
 connected
in series. Determine the value of R for which p.f. of the circuit is 0.8 and also
draw its phasor diagram.
(b) A circuit consisting of a variable resistor in series with a capacitance of 80 F
is connected across a 120V, 50Hz supply. Calculate the value of resistance so
that the power absorbed is 100W. [8 7]
2. List out the main parts of a DC machine and explain with help of neat sketch. [15]
3. Replace the network to the left of terminals ab by its Thevenin's equivalent circuit.
Hence determine I( gure 1). [15]
Figure 1:
4. Determine the current drawn by a 12 V battery with internal resistance o.5 ohm
by the following in nite network shown in gure 2. [15]
Figure 2:

5. How are measuring instruments are classi ed? Also explain the basic issues con-
cerned with the measurement of electrical quantities. [15]
6. (a) Explain in detail O.C and S.C tests to be conducted on a transformer for
calculation of regulation.
(b) The open-circuit test readings on a 400/200 V, single phase transformer con-
ducted from L.V side are : voltage = 200 V; current = 0.7 A ; power = 95 W.
Calculate the no-load circuit parameters referred to H. V side. [9 6]
7. (a) Write the expression for induced emf in a dc generator and clearly de ne all
the terms. What happens if a DC generator is operated at a speed below the
rated speed?
(b) The armature of a 6-pole D.C. generator has a wave winding containing 664
conductors. Calculate the generated emf when the 
ux per pole is 0.06 weber
and the speed is 250 rpm. At what speed must the armature be driven to
generate an emf of 250 V if the 
ux per pole is reduced to 0.058 weber? [15]
8. A rotating magnetic eld is produced in the air gap of a 3-phase induction motor
when a balanced supply is given to the stator. Justify the statement with necessary
mathematical equations and phasor diagrams. [15]
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