Download MODEL EXAM

E.G.S PILLAY ENGINEERING COLLEGE, NAGAPATTINAM
DEPARTMENT OF ECE
MODEL EXAM
Sub.Code & Name: EE6201 & CIRCUIT THEORY
Date
: 30.4.2014
Year & Sem
: I & II (ECE A & B)
Time
: 3 Hours
Staff Name
: S.DURGADEVI
Max. Marks: 100
PART A
Answer all the Questions
(10 x 2 =20)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
State Ohm's law.
A series RLC circuit has R=25Ω,L=0.221H and C=66.3µF with frequency of 60 Hz. Find
the power factor?
Write the expressions for resistances when you transform a star connected network
into delta connected network?
State maximum power transfer theorem for d.c circuits.
Define the term quality factor?
Determine the resonant frequency for a series RLC circuit when R=10Ω, L=0.5µH and
C=10µF?
Write down the expressions for phase and line voltages of a 3 φ balanced system.
A symmetrical 3 φ, 440 V system supplies a balanced delta connected load. The
branch current is 10A at a phase angle of 30˚ lagging. Find the total active power.
In a balanced, 3 φ star connected system, the current through one of the phases is
10∟20˚A. Find the value of three line currents.
List out the methods of power measurement in the 3 φ balanced circuits.
PART B
Answer all the Questions
(16 x 5 =80)
11.a) Determine the total current taken from the source for the circuit shown in figure. (16)
or
11.b) A series circuit has R= 10Ω,L=0.5H and C=10µF and is applied with 50 V,50Hz. Calculate
i)the impedance, ii)the current, iii)the power, iv)the power factor, v)the voltage drops across
each element.
(16)
12.a) Find the current in the 2Ω resistor by the principle of Superposition theorem.
(16)
or
12.b) Find the current through the branch a-b by thevenin's theorem.
13.a) Derive bandwidth for a series RLC circuit as a function of resonant frequency.
(16)
(16)
or
13.b) A series RLC circuit has R=10Ω, L=0.1H and C=10 µF. Find the impedance i)at resonant
frequency, ii)20 Hz above resonant frequency, 20 Hz below resonant frequency, iii)Quality
factor of the coil.
(16)
14.a) A balanced, 3 φ star connected load with impedance (8+j6)Ω per phase is connected
across a symmetrical 400V, 3 φ, 50Hz supply. Determine the line current, power factor of the
load, total power.
(16)
or
14.b) A balanced, 3 φ delta connected load of (4+j8)Ω is connected across a symmetrical 400V,
3 φ, 50Hz supply. Determine the line currents, phase currents and total power.
(16)
15.a) A 3 φ balanced load has 10Ω resistance in each of its phases. The load is supplied by a
220V, 3 φ, 50 Hz supply. Calculate the power absorbed by the load if it is connected in wye,
Calculate the same it is connected in delta.
(16)
or
15. b)Prove that two watt meters are sufficient to measure three phase power.
(16)
PART A
Answer key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
PART B
State Ohm's law.
A series RLC circuit has R=25Ω,L=0.221H and C=66.3µF with frequency of 60 Hz. Find
the power factor?
Write the expressions for resistances when you transform a star connected network
into delta connected network?
State maximum power transfer theorem for d.c circuits.
Define the term quality factor?
Determine the resonant frequency for a series RLC circuit when R=10Ω, L=0.5µH and
C=10µF?
Write down the expressions for phase and line voltages of a 3 φ balanced system.
A symmetrical 3 φ, 440 V system supplies a balanced delta connected load. The
branch current is 10A at a phase angle of 30˚ lagging. Find the total active power.
In a balanced, 3 φ star connected system, the current through one of the phases is
10∟20˚A. Find the value of three line currents.
List out the methods of power measurement in the 3 φ balanced circuits.
11.a) Determine the total current taken from the source for the circuit shown in figure. (16)
Refer Ex:32,page no-1.39
or
11.b) A series circuit has R= 10Ω,L=0.5H and C=10µF and is applied with 50 V,50Hz. Calculate
i)the impedance, ii)the current, iii)the power, iv)the power factor, v)the voltage drops across
each element. Refer Ex:32,page no-1.39
(16)
12.a) Find the current in the 2Ω resistor by the principle of Superposition theorem.
Refer Ex:32,page no-1.39
(16)
or
12.b) Find the current through the branch a-b by thevenin's theorem.Refer Ex:32,page no-1.39
(16)
13.a) Derive bandwidth for a series RLC circuit as a function of resonant frequency.
(16) or
13.b) A series RLC circuit has R=10Ω, L=0.1H and C=10 µF. Find the impedance i)at resonant
frequency, ii)20 Hz above resonant frequency, 20 Hz below resonant frequency, iii)Quality
factor of the coil. Refer Ex:32,page no-1.39
(16)
14.a) A balanced, 3 φ star connected load with impedance (8+j6)Ω per phase is connected
across a symmetrical 400V, 3 φ, 50Hz supply. Determine the line current, power factor of the
load, total power.
Refer Ex:32,page no-1.39
(16) or
14.b) A balanced, 3 φ delta connected load of (4+j8)Ω is connected across a symmetrical 400V,
3 φ, 50Hz supply. Determine the line currents, phase currents and total power.
(16)
Refer Ex:32,page no-1.39
15.a) A 3 φ balanced load has 10Ω resistance in each of its phases. The load is supplied by a
220V, 3 φ, 50 Hz supply. Calculate the power absorbed by the load if it is connected in wye,
Calculate the same it is connected in delta. Refer Ex:32,page no-1.39
(16)
or
15. b)Prove that two watt meters are sufficient to measure three phase power.
(16)