Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
Faculty of Information Engineering & Technology
(IET)
Electronics Engineering Dept.
Course Instructor: Prof. Yasser G. Hegazy
Bar Code
Instructions:
1. Answer all the questions.
2. The exam consists of 5 questions in 11 pages including this page.
3. The exam allowed time is 3 hours.
4. Electronic Calculators are allowed.
5. Clearly show all steps used in your solutions.
Please, do not write anything on this page
Question
Mark
Out of
1
10
2
10
3
10
4
12
5
10
Total
52
1

Final Exam Electric Circuits I”ELCT 301”
Question # 1
Time allowed: 3 hours
[ 10 Marks ]
In the circuit shown in Figure 1, R is a resistance in Ohm. Find the value of R such that the power supplied by the current source is 3200 W.
“Note: the use of Star to Delta transformation is not permitted”
2
Figure 1

Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
3

Final Exam Electric Circuits I”ELCT 301”
Question # 2
Time allowed: 3 hours
[10 Marks]
In the circuit shown in Figure 2, the current in the 6 Ohm resistor is given by i
1
(t) = 20 ( 1- e
-2t
) A t > 0
Find an expression for Vc(t) and ic(t) for t > 0. Assume zero initial conditions for all capacitors.
4
Figure 2

Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
5

Final Exam Electric Circuits I”ELCT 301”
Question # 3
Time allowed: 3 hours
[10 Marks]
The switch in the circuit shown in Figure 3 has been closed for a long time. It opens at t = 0.
[2 Marks] a) The initial value of the capacitor voltage at t =0 b) The final value of the capacitor voltage when t →∞ c) The circuit time constant for t >0
[3 Marks]
[3 Marks] d) The mathematical expression for i

(t) for t > 0.
[2 Marks]
6
Figure 3

Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
7

Final Exam Electric Circuits I”ELCT 301”
Question # 4
Time allowed: 3 hours
[12 Marks]
For the two circuits shown in Figure 4 a) Reduce circuit I (Figure 4(a)) to its Thevenin’s equivalent between a & b. [6 Marks] b) Find

such that maximum power is transferred from circuit I (Figure 4(a)) to circuit II (Figure
4(b)) when nodes a & b of circuit I are connected to nodes a’ and b’ of circuit II.
[4 Marks] c) Calculate the maximum power.
[2 Marks]
Circuit II Circuit I
8
Figure 4(b)
Figure 4
Figure 4(a)

Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
9

Final Exam Electric Circuits I”ELCT 301”
Question # 5
Time allowed: 3 hours
[10 Marks]
For the circuit shown in Figure 5, apply the superposition method to calculate the power supplied/absorbed by each dependent source.
11
Figure 5

Final Exam Electric Circuits I”ELCT 301” Time allowed: 3 hours
11