Download EE2010 - Final Term Exam

Answer the Following Questions:
Question No. (1)
4 marks(16x0.25)
Calculate the Requirements and Choose the Correct Answer:
1- An electric circuit consists of a voltage source V=100 V in series with a resistor R.
If the current flows in the circuit is 10 A, the value of R equals to:
(a) 0.01K
(b) 0.1
(c) 100
(d) 1
2- An electric circuit with resistors 2 , 4 , 6 , and 8  are connected in parallel.
The equivalent resistor equals to:
(a) 0.96 
(b) 0.93 
(c) 0.9 
(d) 0.98
3- An electric circuit consists of a voltage source V=200 V in series with two resistors
of 25 Kand 100 K. The out put voltage across the 100 K resistor equals to:
(a) 120 V
(b) 132 V
(c) 140 V
(d) 160 V
4- An electric circuit consists of a current source with I=20 A and two resistors 16 
and 4 . All elements are connected in parallel. The current flows in the 4  resistor
equals to:
(a) 16 A
(b) 0.16 A
(c) 8 A
(d) 0.8 A
5- An electric circuit consists of a current source with I=8 A and four resistors 80 , 10
, 80  and 24 . All elements are connected in parallel. Using the current division
method, the current flows in the 24  resistor equals to:
(a) 20 A
(b) 2 A
(c) 0.2 A
(d) 0.02 A
6- A delta connection with resistors (100 , 125 , 25 ), the corresponding wye
connection resistors equal to:
(a) (50 , 12.5 , 10 )
(b) (25 , 25 , 20 )
(c) (100 , 25 , 20 )
(d) (150 , 50 , 10 )
1-15
7- For the circuit shown in the Fig. B-1, the Thevenin impedance at terminals a-b is:
(a) 1 Ω (b) 0.5 − j0.5 Ω (c) 0.5 + j0.5 Ω (d) 1 + j2 Ω
(e) 1 − j2 Ω
Fig. 1-7
8- In the circuit of Fig. B-1, the Thevenin voltage at terminals a-b is:
(a) 3.535 − 45◦ V (b) 3.535 45◦ V (c) 7.071 − 45◦ V (d) 7.071 45◦ V
9- The value of the current Io in the circuit in Fig. B-2 is:
(a) 4 0◦ A
(b) 2.4 − 90◦ A (c) 0.6 0◦ A
(d) −1 A
Fig. 1-9
10- The Thevenin impedance of a network seen from the load terminals is (80 + j55) Ω.
For maximum power transfer, the load impedance must be:
(a) (−80+j55) Ω
(b) (−80−j55) Ω
(c) (80−j55) Ω
(d) (80+j55) Ω
11- A certain passive network has equivalent impedance Z=(3+j4) and an applied
voltage v  42.5 cos(100 t  30) V
11-1 The effective voltage equals to:
(a) Veff  42.5l 230 V
(b) Veff  42.530 V
(c) Veff  42.5l 2  30 V
(d) Veff  42.5l 2100 V
2-15
11-2 The effective current equals to:
(a) I eff  8.5  23.13 A
(b) I eff  8.523.13 A
(c) I eff  8.5l 2  23.13 A
(d) I eff  8.5l 230 A
11-3 The complex power equals to:
(a) S  18.0653.13 VA
(c) S  180.653.13 VA
(b) S  361.253.13 VA
(d) S  180.6  53.13 VA
11-4 The average power equals to:
(a) P = 108.4 W (b) P = 1084 W
(c) P = 144.5 W
(d) P = −108.4 W
11-5 The reactive power equals to:
(a) Q = 1445 VAR
(c) Q = −144.5 VAR
(b) Q = 144.5 VAR
(d) Q = 108.4 VAR
11-6 The power factor equals to:
(a) P.F = 0.6 leading
(c) P.F = 0.8 lagging
(b) P.F = 0.6 lagging
(d) P.F = 0
3-15
Question No. (2)
For the circuit shown in Figure (2), find the following:
2(0.5+0.5+0.5+0.5) marks
(a) The current in the 30 resistor using current divider,
(b) The current in the 25 resistor using current division,
(c) The voltage v2 using the voltage divider,
(d) The power associated with the independent source.
12 
50 
30 
+
25 A
v1
+
-
v2
25 
60 
30 
-
Figure (2) Question No. (2)
4-15
Question No. (3)
14 marks
(3-A)
3.5 (1.5+1+1) marks
Use the node-voltage method in the circuit shown in Figure (3-A) to determine the
following:
(a) The power associated with all sources,
(b) The power dissipated in all resistor,
(c) Verify that the power dissipated or absorbed equals to the power delivered in the
circuit shown in Figure (3-A).
4
2
5V
20V
4A
3
5
Figure (3-A) Question No. (3-A)
5-15
(3-B)
3.5 (1.5+0.5+1+0.5) marks
Use the mesh-current method for the circuit shown in Figure (3-B) to find the
following:
(a) The power dissipated in the 2 resistor,
(b) The power associated with the all sources,
(c) The voltage V.
10 A
2
1
+
75 V
ia
V
5
-
Figure (3-B) Question No. (3-B)
6-15
2V
5
(3-C)
4 (2.5+0.5+0.5+0.5) marks
For the circuit shown in Figure (3-C), find the following:
(a) The Thevenin equivalent circuit with respect to terminals (a, b),
(b) The value of the resistor R that enables the circuit shown to deliver the maximum
power to the terminals (a, b),
(c) The maximum power delivered to the resistor R,
(d) If a resistor 150 is connected across the terminals (a, b), find the power
dissipated in this resistor using Thevenin theorem.
20 

160i

a
i
60 
4A
80 
+
40 
b
Figure (3-C) Question No. (3-C)
7-15
(3-D)
3 (1+1+1) marks
For the circuit shown in Figure (3-D), find the following:
(a) The voltage V using source transformation,
(b) The delivered power by the 72 V source, 48 source, and 30 A source,
(c) The power dissipated in the 6 resistor.
12 
4
+
30 A
6A
6
V
-
72 V
48 V
Figure (3-D) Question No. (3-D)
8-15
10 
Question No. (4)
10 marks
(4-A)
3 (1.5+0.5+0.5+0.5) marks
Use the node-voltage method for the circuit shown in Figure (4-A) to find the
following:
(a) The current in each branch,
(b) The voltage across the 20 resistor,
(c) The steady-state expression for the voltage and current across the capacitor,
is=15 cos (t), Vs=200 sin (t), = 4000 rad/sec.
20 
+
is
5
V
9 mF
100 mH
-
Figure (4-A) Question No. (4-A)
9-15
Vs
(4-B)
3 (1.5+0.5+0.5+0.5) marks
Use the mesh-current method for the circuit shown in Figure (4-B) to find the
following:
(a) The steady state expression for current I,
(b) The voltage across the 2 resistor,
(c) The steady-state expression for Vx(t).
1
j2 
I

Vs  33.80 V
3
+
Vx
-j5 
-
Figure (4-B) Question No. (4-B)
10-15
0 . 75 V x
2
(4-C)
4 (2.5+0.5+0.5+0.5) marks
For the circuit shown in Figure (4-C), use the Thevenin theorem to find the following:
(a) The Thevenin equivalent circuit with respect to the terminals (a, b),
(b) The current Ix.,
(c) The power dissipated in the 12 resistor,
(d) The steady state expression for voltage V2.
j2 
j3 
1
1
a
+

1500 V
V1
-
+
+
12 
V2
Ix
-j16 
-
b
Figure (4-C) Question No. (4-C)
11-15
V3


39I x
Question No. (5)
(5-A)
For the circuit shown in Figure (5-A) find the following:
(a) The value of the voltage between the terminals (a, b),
(b) The power dissipated in the 120  resistor,
(c) The voltage across the capacitor.
-j40 
12 
6 marks
3 (2+1+1) marks
120 
a
+
120Ð 0 V
Vx
60 


10 Vx
-
b
Figure (5-A) Question No. (5-A)
12-15
(5-B)
For the circuit shown in Figure (5-B) determine the following:
(a) The voltage across the 2 resistor,
(b) The power dissipated in the 7.5 resistor,
(c) The power associated with all sources.
4
2.5 
2
+
193 V
V
+
0.4V
V
0.5 A
3 (1+1+1) marks


6 -
+
V
7.5 
-
8
Figure (5-B) Question No. (5-B)
13-15
0.8V
Question No. (6)
4 marks (1+1+1+1)
For the circuit shown in Figure (6), a practical voltage source formed by an ideal
voltage source Vg  320 20 in series with an impedance Zg feeds a load ZL.
(a) Find the average power Pg and the reactive power Qg and the apparent power S
delivered by the voltage source,
(b) Find the average power PL and the reactive power QL absorbed by the load.
(c) Find the power factor of the load,
(d) Determine the value of the capacitor that would correct the power factor to unity
if it is placed in parallel with the load.
Note (the source frequency is 60 Hz)
Zg
j100
50
I
j100
Vg=320√2 0°
Load : ZL
200
Figure (6) Question No. (6)
14-15
15-15