1
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY
HYDERABAD
I YEAR B.TECH. Ist MID TERM EXAMINATION
ELECTRICAL CIRCUITS ANALYSIS - 07A1EC02
UNIT-I
1.
Explain the volt-ampere relationship of R, L and C elements in detail.
2.
What is the difference between an ideal source and a practical source? Draw the
relevant characteristics of the above sources.
[5M]
3.
Explain the difference between active elements and passive elements with suitable
examples.
[5M]
4.
Determine the current through 6 Ω resistor and the power supplied by the current
source for the circuit shown in figure below.
[5M]
5.a)
b)
Explain independent and dependent sources in detail.
A voltage given by υ = 6t volts is connected across a 25 Ω resistor. Determine
the energy dissipated by the resistor during the interval 0 ≤ t ≤ 5sec .
[5M]
6.
Define the following I) Resistance ii) Inductance
the V-I relationship for the above elements.
7.a)
A current I = 10e-t is applied to a 2H inductor what is the respective voltage
across inductor?
Compare the properties of inductance and capacitance.
[5M]
b)
[5M]
iii) Capacitance. Also, give
[5M]
Contd…2
2
8.
A capacitor of 1F is applied with a voltage waveform shown in figure below.
Obtain the current and energy waveforms in the capacitor.
[5M]
9.
Explain the source transformation used in electrical networks with relevant
examples.
[5M]
10.
Using network reduction, find the voltage V in figure below.
11.
Using source transformation, find the equivalent network containing only one
voltage source and a resistance at the terminals 1, 2.
[5M]
[5M]
Contd…3
3
12.
State and explain Kirchoff’s laws?
[5M]
13.
For the circuit shown in figure below, find the current through 20 Ω resistor?
14.
Find the current through 10 Ω resistor in the circuit shown in figure below. [5M]
15.
Find the equivalent resistance between terminals A and B of figure below.[5M]
Contd…4
4
16.
Reduce the network shown in figure below, to a single loop network by source
transformation, to obtain the current in the 12 Ω resistor.
[5M]
17.
Using kirchoff’s current law, find the values of current i1 and i2 in the circuit
shown in figure below.
[5M]
18.a) Explain i) Practical voltage source and
ii) Ideal voltage source.
b) State the advantages of source-transformation technique in electrical circuits.
[5M]
19.
Determine the resistance between the terminals A and B of the circuit shown in
figure below.
[5M]
Contd…5
5
20.
Determine the current supplied by each battery in the circuit shown in figure
below, by using Kirchoff’s laws.
[5M]
21.
Find the current in each resistor and the total current taken by the network shown
in figure below.
[5M]
22.
Obtain the expressions used in conversion of y to ∆ transformation.
[5M]
23.
Obtain the expressions used in conversion of ∆ to y transformation.
[5M]
24.
A 20v battery with an internal resistance of 50ohms is connected to a resistor of ×
ohms. If an additional resistance of 6 Ω is connected across the battery, find the
value of × , so that the external power supplied by the battery remain the same.
[5M]
Calculate the resistance between A and B terminals of the network shown in
figure below.
[5M]
25.
Contd…6
6
26.
What is dependent source? What are the various types of dependent sources?
Draw the V-I characteristics of the above sources?
[5M]
27.
What are passive and active elements? Explain the volt-ampere relationship of the
above elements.
[5M]
28.
A current waveform shown in figure below is applied to a capacitor of value
2 µ F. Find the voltage waveform.
[5M]
29.
Find the current through the 3 Ω resistance using Kirchoff’s laws, in figure
below.
[5M]
30.
Find RAB in the network shown in figure below.
[5M]
Contd…7
7
31.
Find the voltage and current source equivalent representation of the following
network across AB, as shown in figure below.
[5M]
32.
Three resistances each of 5 Ω , 10 Ω , 15 Ω are connected in parallel and supplied
by 150V d.c. Find the ratio of currents in each branch, power drawn by the circuit
and power consumed in each branch.
[5M]
33.
Find the value of applied d.c. voltage for the network, shown in figure below.
[5M]
34.
Find the current through each element in the network shown in figure below using
network reduction technique.
[5M]
Contd…8
8
35.
Find the equivalent resistance as viewed from terminals A & B in the network
shown in figure below.
[5M]
36.
Determine the current through each element in the network shown in figure
below.
[5M]
37.
Find the current through each element in the network as shown in figure below by
network reduction technique.
[5M]
Contd…9
9
38.
A wheat stone bridge ABCD is arranged as follows;
AB=20 Ω , BC=10 Ω , CD=5 Ω and DA=50 Ω . A galvanometer of resistance
60 Ω is connected between B and D. A 100 volts supply is connected between A
and C with C positive. Find the power dissipated through galvanometer
resistance.
[5M]
39.
Find ‘V’ in figure below using the network reduction technique.
[5M]
40.
Find the input resistance of the circuit shown in figure below.
[5M]
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10
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY
HYDERABAD
I YEAR B.TECH. Ist MID TERM EXAMINATION
ELECTRICAL CIRCUITS ANALYSIS - 07A1EC02
UNIT-II
1.
Explain the following terms:
a) Magnetic circuit
d) Reluctance
b) Permeability
e) Flux.
c)MMF
[5M]
2.
An ironing of mean length 50cms has an airgap of 1 mm and a winding of 200
turns. If the relative permeability of iron is 500 when a current of 1A flows
through the coil, find the flux density?
[5M]
3.
State and explain the Faraday’s law of electromagnetic induction?
4.
A cast steel ring has a circular cross section in diameter and a mean circumference
of 80 cm. The ring is uniformly wound with 600 turns.
Estimate the current required to produce a flux of 0.5 mwb in the ring.
[5M]
5.
Find the total inductance of the three series coupled coils as shown in figure
below.
[5M]
6.a)
b)
Explain
i) self inductance
ii) mutual inductance.
Define leakage factor and its effect in a magnetic circuit.
7.
State and explain
i) Statically induced emf
8.
ii) Dynamically induced emf
[5M]
[5M]
iii) Lenz’ law.
[5M]
The combined inductance of two coils connected in series is 0.6 H or 0.1H,
depending upon the relative directions of the currents in the coils. If one of the
coils when isolated has a self inductance of 0.2 H. Calculate
i) Mutual inductance and
ii) The coefficient of coupling.
[5M]
11
Contd…2
9.
Derive the expression for coefficient of coupling between two magnetically
coupled coils interms of their self and mutual inductance.
[5M]
10.
For the circuit shown in figure below, find the coefficient of coupling and place
the dots so that the power output of the source is 240 watts.
[5M]
11.
Write short notes on dot convention used in magnetically coupled coils.
[5M]
12.a) Define i) Magnetising force
ii) Flux density
b) Derive the expression of equivalent inductance of two series connected coupled
coils.
[5M]
13.a) Compare magnetic circuit with electric circuit in any eight aspects.
b) Derive the expression of equivalent inductance of two parallel connected coupled
coils (aiding).
[5M]
14.
In the network shown in figure below, L1 = 2H, L2 = 4H, M = 2.4 H. Assuming
the inductance coils to be ideal, find the amount of energy stored after 0,2 sec of
the circuit connected to a d.c. source of 10V.
[5M]
15.
Two coupled coils have self inductances, L1 = 10m H and L2 = 20m H. The
coefficient of coupling is 0.5. Find the voltage in the second coil and the flux of
first coil provided the second coil has 500 turns and the circuit current is given by
i1 = 2 sin ¾ t amperes.
[5M]
12
Contd...3
16.
Explain the physical basis of the dot convention used in magnetically coupled
coils.
[5M]
17.
Determine the inductance between the terminals for a three coil system shown in
figure below.
[5M]
18.
Derive the relationship between the self, mutual inductances and coefficient of
coupling?
[5M]
19.
Derive the expressions for self inductance and mutual inductance interms of
number of turns, flux and current in a coupled circuit.
[5M]
20.
A ring shaped electromagnet has an air gap of 6mm and 20cm2 in area, the mean
length of the core being 50cm and its cross section is 10cm2. Calculate the
ampere-turns required to produce a flux density of 0.6 wb/m2 in the air gap.
Assume the permeability of iron is 1200.
[5M]
21.
A coil of 150 turns is linked with a flux of 0.01 wb when carrying a current of
20A, calculate the inductance of the coil. If this current is uniformly reversed in
0.02 sec, calculate the induced emf?
[5M]
22.
Two coupled coils of L1 = 0.8 H and L2 =0.2 H have a coupling coefficient of
N
K = 0.9. Find the mutual inductance M and the turns ratio 1 .
[5M]
N2
A coil of inductance 210 MH is magnetically coupled to another coil of
inductance 820 mH. The coupling coefficient is 0.6. Calculate the equivalent
inductance of the following circuit combinations
a) series aiding b) series opposing
c) parallel aiding
d) parallel opposing.
[5M]
23.
Contd.…4
13
24.
What is magnetic circuit? Bring out the analogy between electric circuit and
magnetic circuit.
[5M]
25.
Two coils having 30 and 60 turns are wound side by side on a closed iron circuit
of 100 cm2 cross-section and mean length 150cm. Calculate
i)
the self inductance of the two coils and mutual inductance if relative
permeability of iron is 2000.
ii)
Calculate coefficient of coupling.
[5M]
26.
A flux density of 0.5 T is created in a magnetic core when magnetic field strength
is 800 A T/m. The core has a length of 0.3 m and cross sectional area of 8 cm2.
Find i) MMF
ii) Relative permeability iii) Flux
iv) Reluctance. [5M]
27.
What is coefficient of coupling? What is the range of variation of this quantity?
In which type of circuits is it minimum and in which type of circuits is it
maximum?
[5M]
28.
Two inductors have self inductance of 0.1 mH and o.4 mH and a mutual
inductance of 0.15mH. What is the value of coefficient of coupling between
them? If a current of I(t) = 3sint + 1.5 sin2t is passed through the first inductor,
what is the expression for the voltage induced in the second coil?
[5M]
29.
The combined inductance of two coils connected in series are 0.6 H and 0.1 H in
series aiding and series opposing connections. If the self inductance of each coil is
0.2H, find the coefficient of coupling?
[5M]
30.a) Explain the concept of mutual inductance?
b) The current in a coil is changing at a rate of 2 A/sec. The voltage across another
coil placed near to it was found to be 10 mv. What is the value of mutual induced
between the two coils?
[5M]
31.
Coil 1 of pair of coupled coils has a continuous current of 5A and the
corresponding fluxes φ11 and φ12 are 0.2 mwb and 0.4 mwb respectively. If the
[5M]
turns are N1 = 500, N2 = 1500. Find L1, L2, M and K.
32.a) Derive an expression for the energy stored in an inductor.
b) Give the significance of coefficient of coupling.
33.
[5M]
A steel ring 10 cm radius and of circular cross section 1cm is radius has an air gap
of 1mm length. It is wound uniformly with 500 turns of wire carrying a current of
3A. Neglect magnetic leakage. The air gap takes 60% of the total mmf. Find the
total reluctance.
[5M]
Contd…5
14
34.
An iron ring 10 cm diameter and 15cm2 cross section is wound with 250 turns of
wire for a flux density of 1.5 wb/m2 and permeability 500. Find the exciting
current, the inductance and the stored energy?
[5M]
35.
An air cored solenoid 1m long and 10 cm in diameter has 500 turns. Calculate
i) the inductance ii) energy stored in it when a current of 2A passes through it.
[5M]
36.
A coil consists of 1500 turns and a current of 5A in the coil gives rise to a
magnetic flux of 1000 µ b . Calculate the inductance of the coil and determine the
average emf induced in the coil when the current is reversed in 0.01 sec. [5M]
37.
Obtain the formula for the total inductance when the two coils are connected in
i) Series Aiding
ii) Parallel Aiding.
38.
Obtain the formula for the total inductance when the coils are connected in
i) Series opposing
ii) Parallel opposing.
[5M]
39.
Two coils × of 1200 turns and y of 1500 turns lie in parallel planes, so that 50%
of flux produced by × links y. A current of 5A in × produces 0.05 mwb, while
the same current in y produces 0.075 mwb. Find the mutual inductance and the
coefficient of coupling?
[5M]
40.
A coil consists of 1000 turns of wire uniformly wound on a non- magnetic ring of
mean diameter 500 mm and a cross sectional area of 1000 mm2. Calculate
i)
the inductance of the coil
ii)
the energy stored in the magnetic field when the coil is carrying a current
of 10A.
[5M]
41.
Draw the dotted equivalent circuit for the coupled coils as shown in figure below
and find the equivalent impedance of the series circuit between A and B.
[5M]
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