I B.Tech - Regular Examinations, June 2009
First Year
BASIC ELECTRICAL ENGINEERING- SET NO: 2
(Regulation 2007)
Time : 3 hours |
Maximam Marks:80 |
Answer any FIVE Questions
1. (a) Explain in detail how a magnetic field is produced due to the electric current.
(b) By applying kirchoffs law, find the current through all the elements in the
circuit asc shown in the figure 1.
2.Calculate the current through 2+j3
impedance by superposition theorem as shown in figure 2.
3.(a) Explain as to what you understand by
i. Static
ii. Dynamic inducement of electromot ive force. Illustrate by the help of
simple sketches.
(b) A coil of 100 turns is linked by a magnetic flux of 20mwb. If this magnetic
flux is reversed in a time of 2ms, calculate the average emf induced.
4.An inductive coil of resistance 12
and inductance 0.0398 H is connected in parallel
with a capacitive branch having resistance of 20
and capacitance of 265.2 µF. The
combination is connected across 220 V, 40 Hz mains. Calculate the total current taken by the combination. It is desired to raise the power factor of the combination
as such a capacitor of capacitance 67.5 µF is connected in parallel with the above
combination. Find the power factor of the resultant circuit.
5.A 20 KVA , 2000/200V transformer has an iron loss of 300W and full load copper
loss of 400 W. During the day it is loaded as follows: ![](images/bee6.jpg)
Find the all day efficiency.
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 3 phase, 4 pole 50 Hz induction motor at standstill has 120 V induced across its
star connected terminals. The rotor resistance and standstill reactance per phase
are 0.2
and 0.1
respectively. Calculate the speed when the rotor is drawing a
current of 16 A at a particular load. Also calculate the speed at which the torque
is maximum and the corresponding value of the rotor.
8.What are the basic requirements of indicating instrument? Briefly discuss them.
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