I B.Tech - Regular Examinations, June 2009
First Year
BASIC ELECTRICAL ENGINEERING- SET NO: 3
(Regulation 2007)
Time : 3 hours |
Maximam Marks:80 |
Answer any FIVE Questions
1. (a) Determine the power output of each voltage source using kirchoffs laws for the
network as shown in figure 1.
(b) By applying kirchoffs law, find the current through all the elements in the
circuit asc shown in the figure 1.
2.(a) Give a detailed comparison of series and parallel circuit.
(b) What are the applications, merits and demerits of a series circuit?
(c) What are the applications and advantages of a parallel circuit?
3.(a) State and explain faraday’s laws of electromagnetic induction.
(b) Write short notes on Lenz’s law.
(c) A coil of 1000 turns of wire uniformly wound on a non-magnetic ring of mean
diameter 40 cm and cross-sectional area 20 sq.cm. Calculate
i. The inductance of the coil.
ii. The energy stored in the magnetic field when the coil is carrying a current
of 15A.
iii. The emf induced in the coil if this current is completely interrupted in
0.01 second.
4.An inductive coil of resistance 20
and reactance 31.4
is connected in parallel
with a capacitance of 72.1 µF across a 100 V, 50Hz supply. Find the total current,
power factor, power absorbed. Draw the phasor diagram of the circuit.
5.(a) A 400/200V single phase transformer is supplying a load of 50A at a power
factor of 0.866 lagging. The no load current is 2 A at 0.208 power factor
lagging. Find the primary current and primary power factor. (b) Draw the phasor diagram of a transformer on load when it is taking
i. Resistive load.
ii. Inductive load.
iii. Capacitive load.
6.(a) How is the efficiency of the dc motor determined by the direct loading method?
Derive the equation for efficiency.
(b) In a brake test on a dc shunt motor full load readings are as follows. Tension
on tight side is 9.1 Kg, tension on slack side is 0.8 Kg. Total current is 10 A,
supply voltage is 110V, speed is 132 rpm, effective radius of the pulley is 7.5
cm. Calculate its full load efficiency.
7.(a) Derive the equation for torque of a three phase induction motor.
(b) A three phase slip ring induction motor gives a reading of 55 V across the slip
rings on a open circuit, when at rest with normal stator voltage applied. the
rotor is star connected and has an impedance of 0.7+j5
/ph. Find the rotor
current when the machine is
i. At standstill with slip rings joined to a star connected starter with phase
impedance of 4+j3
and
ii. Running normally with 5% slip.
8.(a) Bring out the advantages and disadvantages of MI and MC instrument.
(b) Bring out the differences between various methods of producing controlling
torque.
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