Download Visvesvaraya Technological University (VTU) BE/B.Tech First And Second Semester (1st sem and 2nd sem) 20192020 Jan ( Bachelor of Engineering) 15 Scheme 5ELE1525 Basic Electrical Engineering Previous Question Paper
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First/Second Semester B.E. Degree Examination,
Basic Electrical Engineering
Time: 3 hrs. Max. Marks: 80
Note: Answer any FIVE full questions, choosing ONE Oil question from each module.
Module1
1 a. State Ohm's law and mention its limitations. (04 Marks)
b. Derive an expression for energy stored in a magnetic field. (06 Marks)
c. A circuit of two parallel resistors having resistance of 205 and 30Q respectively connected
in series with 150 resistor. If the power dissipation in 150 resistor is 135 watts, find:
to
i) Current in 2051, and 300 resistors
ii) Voltage across whole circuit and
in) Power consumed in 200 resistor. (06 Marks)
r.)
CC cc
OR
2 a. State and explain Kirchoff s laws. (04 Marks)
b. A coil consists of 600 turns and a current of 10A in the coil gives rise to a magnetic flux of
l m wb. Calculate: i) Self inductance ii) Induced emf iii) Energy stored when the current
is reversed in 0.01 second. (06 Marks)
c. A coil of 1000 turns is wound on a silicon steel ring of relative permeability 1200. The ring
has mean diameter of 10cms and crosssectional area of 12cm
2
. When a current of 4 ampere
flows through the coil, find:
i) Flux in the coil
ii) Inductance of the coil
iii) The emf induced in the coil if the flux falls to zero in 15 milliseconds
iv) Now if another similar coil is placed such that 70% magnetic coupling exists between
the coils, find the mutual inductance. (06 Marks)
4.= :D
Module2
i.3 3 a. Explain the working principle of D.C. generator. (04 Marks)
i72,
b. Explain working principle of dynamometer type of wattmeter. (06 Marks)
? a.)
c. The field resistance and armature resistance of a 500V, 4 pole wave connected of a 500V, 4
7 5
pole wave connected dc shunt motor are 250 ohm and 0.1 ohm respectively. The armature
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.= z
has 492 conductors and flux per pole is 0.05 wb. Calculate the speed and torque when the
a p, full load current is 20 amps. (06 Marks)
O a.).
0 ?
OR
4 a. Derive equation for the torque developed in the armature of a D.C. motor. (04 Marks)
b. With neat diagram, explain the working principle of inducting type energy meter. (06 Marks)
c. A 4 pole 1500 rpm dc generator has cup wound armature having 24 slots with 10 conductors
per slot. if the flux per pole is 0.04 wb, calculate the e.m.f generated in the armature. What
E
would be the generated emf if the winding is wave connected?
(06 Marks)
USN
5ELE15/25
9/Jan.2020
1 of 2
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c
7
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CI) c
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6 7
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\
First/Second Semester B.E. Degree Examination,
Basic Electrical Engineering
Time: 3 hrs. Max. Marks: 80
Note: Answer any FIVE full questions, choosing ONE Oil question from each module.
Module1
1 a. State Ohm's law and mention its limitations. (04 Marks)
b. Derive an expression for energy stored in a magnetic field. (06 Marks)
c. A circuit of two parallel resistors having resistance of 205 and 30Q respectively connected
in series with 150 resistor. If the power dissipation in 150 resistor is 135 watts, find:
to
i) Current in 2051, and 300 resistors
ii) Voltage across whole circuit and
in) Power consumed in 200 resistor. (06 Marks)
r.)
CC cc
OR
2 a. State and explain Kirchoff s laws. (04 Marks)
b. A coil consists of 600 turns and a current of 10A in the coil gives rise to a magnetic flux of
l m wb. Calculate: i) Self inductance ii) Induced emf iii) Energy stored when the current
is reversed in 0.01 second. (06 Marks)
c. A coil of 1000 turns is wound on a silicon steel ring of relative permeability 1200. The ring
has mean diameter of 10cms and crosssectional area of 12cm
2
. When a current of 4 ampere
flows through the coil, find:
i) Flux in the coil
ii) Inductance of the coil
iii) The emf induced in the coil if the flux falls to zero in 15 milliseconds
iv) Now if another similar coil is placed such that 70% magnetic coupling exists between
the coils, find the mutual inductance. (06 Marks)
4.= :D
Module2
i.3 3 a. Explain the working principle of D.C. generator. (04 Marks)
i72,
b. Explain working principle of dynamometer type of wattmeter. (06 Marks)
? a.)
c. The field resistance and armature resistance of a 500V, 4 pole wave connected of a 500V, 4
7 5
pole wave connected dc shunt motor are 250 ohm and 0.1 ohm respectively. The armature
? 0
.= z
has 492 conductors and flux per pole is 0.05 wb. Calculate the speed and torque when the
a p, full load current is 20 amps. (06 Marks)
O a.).
0 ?
OR
4 a. Derive equation for the torque developed in the armature of a D.C. motor. (04 Marks)
b. With neat diagram, explain the working principle of inducting type energy meter. (06 Marks)
c. A 4 pole 1500 rpm dc generator has cup wound armature having 24 slots with 10 conductors
per slot. if the flux per pole is 0.04 wb, calculate the e.m.f generated in the armature. What
E
would be the generated emf if the winding is wave connected?
(06 Marks)
USN
5ELE15/25
9/Jan.2020
1 of 2
15ELE15/25
5 a.
b.
c.
Module3
Prove that in a purely inductive circuit the current lags voltage by 90?. (06 Marks)
With the help of circuit diagram, explain the two way control of 1 amp. (04 Marks)
A 250 volts at 50Hz is applied across R.C. series, circuit. The current of 2.2A flowing
through it causes a power loss of 96.8 watts in the resistor, power loss of 96.8 capacitor is
negligible. Calculate the resistance and capacitance. Also find the p.f of the circuit.
(06 Marks)
OR
6 a. Define average and r.m.s values of an alternating current. (04 Marks)
b. Define the following:
i) Fusing current
ii) Rated current of fuse and
iii) Fusing factor. (04 Marks)
c. Two impedances z
i    
(150 + j157) ohm and z2 = (100 ? j110) ohm are connected in parallel
across 220V, 50Hz supply. Find the total current, total power drawn and power factor.
(08 Marks)
Module4
7 a. Obtain relationship between line and phase values of voltage in a three phase balanced star
connected system. (06 Marks)
b. Derive the E.m.f equation of an alternator. (06 Marks)
c. A 3phase delta connected load consumes a power of 60kW taking a lagging current of
200A at a line voltage of 400V, 50Hz, find the parameters of each phase. (04 Marks)
OR
8 a. Show that in a three phaSe gar connected balanced circuit two wattmeters are sufficient to
measure the total power. Also obtain expression for power factor of the circuit. (08 Marks)
b. A 3 phase, 16 pole alternator has star connected winding with 144 slots and 10 conductors
per slot. The flux per pole is 0.03wb and the speed is 375rpm. Find the frequency, the phase
emf and line emf Assume pitch factor k
e
= 1 and distribution factor kd = 0.96. Also
determine the output KVA of the alternator. If the total current in phase is 40A. (08 Marks)
Module5
9 a. Derive emf equation of a transformer. (04 Marks)
b. Derive the relation ship between the frequency of the rotor induced emf and the frequency of
the supply given to the stator. (04 Marks)
c. A 500KVA, transformer has an efficiency of 92% at full load, unity power factor and at half
full load, 0.9 power factor. Determine its efficiency at 80% of full load and 0.95 power
factor. (08 Marks)
OR
10 a. Explain the various losses in a transformer and how to minimize them. Give equations for
these losses. (06 Marks)
b. A 250 KVA, 11000/415V, 50Hz single phase transformer has 80 turns on the secondary.
Calculate: i) Maximum value of flux ii) Rated current in primary and secondary. (04 Marks)
c. An 8 pole alternator runs at 750 rpm supplies power to 4 pole induction motor. The
frequency of rotor is 1.5Hz. What is the speed of the motor? What is t (06 Marks)
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This post was last modified on 02 March 2020