Download VTU ((Visvesvaraya Technological University) B.E/B-Tech 2019 July ( Bachelor of Engineering) First & Second Semester (1st Semester & 2nd Semester) 2018 Jan 2017 Dec 17ELE15 Basic Electrical Engineering Question Paper
USN _[
17ELE15
First Semester B.E. Degree Examination, Dec.2017/Jan.2018
Basic Electrical Engineering
Time 3 hrs. Max. Marks: 100
Note: Answer any. FIVE full questions, choosing one full question .from each module.
OR .
2 a. Define dynamically induced e.m.f arid statically induced e.m.f with example l. (06 Marks)
b. Two resistors connected in parallelacross 00V D.0 supply. The total current fi
-
om the
supply source is 10 A. The power disSipated
.
in one resistor is 600 W. What is the current
drawn when they are connected in series across the same supply. (08 Marks)
-c. Define the co-efficient of coupling and:find- its relation-with L1, L., and M. (06 Marks)
MOdule-2
3 a. With a neat sketch, explain the construction of the various parts of a D.0 generator.
(08 Marks)
li
*
. What is the significance of back E1V1F in a D.0 motor? (06 Marks)
)c
, c. With a neat figure, explain the construction and working principle of a dynamometer type
--
- wattmeter.
- (06 Marks)
-111i
wattmeter .
OR
4 a. Derive the EMF equation of D.0 generator. (06 Marks)
b. Find the useful fiuk per pole of a 250V, 6 pole shunt motor (D,C) having a two circuit
connected armature winding with 220 conductors. At normal working temperature, the
overall armature resistance including brushes is 0.2 O. The armature= current is 13.3 A at the
no-load speed of 908 rpm. (08 Marks)
c. Describe with a neat sketch, the constructional details and operation of a single phase
induction typo energy meter. (06 Marks)
Module-1. .
1 a. State Ohm's law. Menton its limitations.
;
.
(05 Marks)
b. - State and explain Kirchoff,s laws as applied to. D.0 circuits.. , (08 Marks)
c. A coil of 150 turns is linked with a_ flux of
-
0,01
.
weber when carrying a current of 10 A.
Calculate
-
the
--
inductanCe
-
or the coil. If the current' is uniformly reversed in 0.01 sec, -
? ? calculate
-
the induced diOUtOrtiOtiVe forCd." - - - - ---'-? , (07 Marks)
li
t
Module-3
5 a. Derive an expression for power in pure capacitor
power waveforms.
b. A series circuit with a resistor of 100 n, capacitor
connected across 220 V, 50 Hz supply. Calculate
factor of the circuit.
c. With a neat sketch, explain 3-way control of Lamp.
OR
circuit and draw voltage, current and
(07 Marks)
of 25 1.1F and inductance of 0.15 H is
impedance, current, power and power
(08 Marks)
(05 Marks)
1 of 2
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USN _[
17ELE15
First Semester B.E. Degree Examination, Dec.2017/Jan.2018
Basic Electrical Engineering
Time 3 hrs. Max. Marks: 100
Note: Answer any. FIVE full questions, choosing one full question .from each module.
OR .
2 a. Define dynamically induced e.m.f arid statically induced e.m.f with example l. (06 Marks)
b. Two resistors connected in parallelacross 00V D.0 supply. The total current fi
-
om the
supply source is 10 A. The power disSipated
.
in one resistor is 600 W. What is the current
drawn when they are connected in series across the same supply. (08 Marks)
-c. Define the co-efficient of coupling and:find- its relation-with L1, L., and M. (06 Marks)
MOdule-2
3 a. With a neat sketch, explain the construction of the various parts of a D.0 generator.
(08 Marks)
li
*
. What is the significance of back E1V1F in a D.0 motor? (06 Marks)
)c
, c. With a neat figure, explain the construction and working principle of a dynamometer type
--
- wattmeter.
- (06 Marks)
-111i
wattmeter .
OR
4 a. Derive the EMF equation of D.0 generator. (06 Marks)
b. Find the useful fiuk per pole of a 250V, 6 pole shunt motor (D,C) having a two circuit
connected armature winding with 220 conductors. At normal working temperature, the
overall armature resistance including brushes is 0.2 O. The armature= current is 13.3 A at the
no-load speed of 908 rpm. (08 Marks)
c. Describe with a neat sketch, the constructional details and operation of a single phase
induction typo energy meter. (06 Marks)
Module-1. .
1 a. State Ohm's law. Menton its limitations.
;
.
(05 Marks)
b. - State and explain Kirchoff,s laws as applied to. D.0 circuits.. , (08 Marks)
c. A coil of 150 turns is linked with a_ flux of
-
0,01
.
weber when carrying a current of 10 A.
Calculate
-
the
--
inductanCe
-
or the coil. If the current' is uniformly reversed in 0.01 sec, -
? ? calculate
-
the induced diOUtOrtiOtiVe forCd." - - - - ---'-? , (07 Marks)
li
t
Module-3
5 a. Derive an expression for power in pure capacitor
power waveforms.
b. A series circuit with a resistor of 100 n, capacitor
connected across 220 V, 50 Hz supply. Calculate
factor of the circuit.
c. With a neat sketch, explain 3-way control of Lamp.
OR
circuit and draw voltage, current and
(07 Marks)
of 25 1.1F and inductance of 0.15 H is
impedance, current, power and power
(08 Marks)
(05 Marks)
1 of 2
I7ELE15
6 a. Define earthing. Explain any one type of earthing with a neat diagram. (06 Marks)
b.
Two impedances (150 - 157j)C2 and (100 + 110j)0 are connected in parallel across 200 V,
50 sapply. Find branch currents, total current and total power consuined in the circuit.
Draw the phasor diagram. (08 Marks)
c. Define power-factor and mention its practical importance. (06 Marks)
Module-4
7 a. In a three phase starconnection, find the relation between line and phase values of currents
and voltages. Also derive the equation for three phase power. (06 Marks)
? .
.b. - -Show that the-two w attmeters are sufficient to measure three phase power. Also-derive an
--
1
- expression for the power'factor in terms of wattmeter readings. - - ? (06 Marks)
. c. A 6 pole, 3 phase, stars?connected alternator has an armature with 90 slots and 12 conductors
_
' - per slot. If revolves at 1000 'rpm, the flux per pole being 0.5 web.' Caleulate the emf
generated, if the winding, factor is 0.97 and all the conductors in each phase are in series.
The coil is full pitched.
,
(08 Marks)
8 a. Mention the advantages of three phase systemover single phase system. (06 Marks)
b. With neat sketches, explain the construction of salient pole alternator. (07 Marks)
c. A three phase load of three equal impedances connected in delta across a balanced 400 V
- --
supply
takes aline current of 1G
-
A,
-
at a power factor of 0.7 lagging. Calculate
(1) The phase current, (ii) Total power, (iii) The total reactive volt Ampers. (07 Marks)
Module-5
9 a. Derive EMF equation of transformer. (06 Marks)
15: The maximum efficiency at full load and upf of a single phase 25 kVA, 500/1000 V, 50 Hz
\ transformer is 98%. Determine the ef ficiency at (i) 75% load 0.9 p.f (ii) 50% load 0.8 p.f
(iii) 25% load 0.6 p.f. (07 Marks)
c. A three phase 6 pole 50 Hz induction motor has a slip of 1% at No-load and 3% at full load.
Determine (i) synchid
-
nous speed (ii) No-load speed (iii) Full load speed (iv) Frequency
of rotor current at ta.nd still (v) Frequency of rotor of rotor current at full load. (07 Marks)
OR
10 a. Derive the coriditiO for which the efficiency of a transformer is maximum. (06 Marks)
b. Define slip. DeriVe an expression for frequency of Rotor current. (06 Marks)
c. A single phase, 20 kVA transformer has 1000 primary turns and 2500 ''secondary turns. The
net cross-sectional area of the core is 100 cm
2
. When the primary winding is connected to
550 V,
-
50`E-1z supply. Calculate (i) The maximum value of the flux density in the core
(ii) the voltage induced in the secondary winding and (iii) The primary and secondary full
load currents. ( 48 Marks)
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This post was last modified on 01 January 2020