*
* 3 2 3 8 *
C09–EC– 306
3238
BOARD DIPLOMA EXAMINATION, (C–09)
MARCH/APRIL—2017
DECE—THIRD SEMESTER EXAMINATION
CIRCUIT THEORY
Time : 3 hours ] [ Total Marks : 80
PART—A 3×10=30
Instructions : (1) Answer all questions.
(2) Each question carries three marks.
(3) Answers should be brief and straight to the point
and shall not exceed five simple sentences.
1. Differentiate between DC and AC.
2. Write the expression for the resonant frequency of the following
parallel circuits :
(a) L, C
(b) RL, C
*
(c) L, RC
3. Find the resonant frequency in the ideal parallel LC circuit
shown below :
/3238
* 1 [ Contd...
WWW.MANARESULTS.CO.IN
4. Define the *following terms :
(a) Junction
(b) Branch
(c) Loop
5. Define the following :
(a) Driving point admittance
(b) Transfer admittance
6. In the circuit shown below, find the value of RL necessary to
obtain maximum power in RL . Also find the maximum power
in RL :
7. A constant current source develops a terminal voltage of 9 V
when a 500-W resistor is connected across its terminals. What
is its terminal voltage, when the 500-W resistor is replaced by a
1·5-kW resistor?
8. When are double humps formed in the frequency response of a
* double-tuned circuit?
9. Write the expressions for the following parameters of low-pass
RC circuit :
(a) Upper 3dB frequency
(b) Rise time in terms of upper 3dB frequency
10. Draw the high-pass R-C circuit and low-pass R-C circuit.
/3238
* 2 [ Contd...
WWW.MANARESULTS.CO.IN
* PART—B 10×5=50
Instructions : (1) Answer any five questions.
(2) Each question carries ten marks.
(3) Answers should be comprehensive and the criterion
for valuation is the content but not the length of
the answer.
11. For the circuit shown below, determine the total current, the
phase angle and total impedance in the circuit :
100 mF
IC
IT
IR 50 W
100 V 50 Hz
12. (a) Explain the V-I characteristics of a series LC circuit with
a.c. source.
(b) A sinusoidal voltage v (t) = 100 sin100t is applied across a
pure inductive coil of inductance L = 0 × 01 H. Determine
(i) current i (t) and (ii) instantaneous power p (t).
13. Determine the power absorbed by 5 W resistor in the circuit
shown below by using mesh analysis :
*
14. Write the node voltage equations for the network shown below
and express them in matrix form :
/3238
* 3 [ Contd...
WWW.MANARESULTS.CO.IN
15. Obtain the*Norton’s equivalent network at AB for the network
shown below :
16. By the superposition theorem, calculate the current through
the 3 + j 4 impedance branch of the circuit shown below :
17. Two coils with inductances in the ratio of four to one have
coupling coefficient k = 0 × 6. When these coils are connected in
series aiding, the equivalent inductance is 44·4 mH. Find L 1, L 2
and M.
18. The switch in the following figure is closed at t = 0. Write the
mathematical expressions for V L (t), i (t) and V R (t) after the
switch is closed :
*
HHH
/3238
* 4 AA7(A)—PDF
WWW.MANARESULTS.CO.IN
