Mansoura University

Faculty of Engineering
Electrical Engineering Department
For second year students- Computer Science
Academic Year 2022/2023 Electric Circuits II- ELE241 Engineering (CSE) Program

First Semester Model (1)- 6 pages Total Marks: 20

Date: 19/11/2022 Mid Term Exam Allowed Time: 60 Minutes
➢All points have an equal weight.
Choose the correct answer:
1- Time constant is the time taken for response to rise…………of maximum value?
a) 100% b) 37.8% c) 63.2% d) 68.3%
2- In which of the following responses oscillations are not present?
a) Under b) Over c) Critical d) Both (a) and (b)
damping damping damping
3- If the roots of an equation are real and equal, the kind of response will be…..
a) Under b) Over c) Critical d) Any of the above
damping damping damping
4- In RLC series circuit R = 2Ω, L = 2mH and C = 1μF, the time constant of the
circuit is……
a) 1 μsec b) 2 msec c) 2 μsec d) 4 msec
5- In RLC series circuit with R = 2Ω, L = 2mH and C = 1μF and applied voltage is
10V DC, the steady state current value is ……
a) 5A b) 2A c) 1A d) 0A
6- In ideal system, coefficient of magnetic coupling (k) is……
a) 0 b) 1 c) ∞ d) Any of the above
7- Two coils (with self-inductances of 10 mH and 15 mH) have an equivalent
inductance of 40 mH when connected in series aiding. What will be the equivalent
inductance if we connect them in series opposing.
a) 20 mH. b) 5 mH. c) 0 mH. d) 10 mH.
8- A 1 mF capacitor is charged by a constant 10 mA current source which is turned
on for 1 second. Assuming the capacitor is initially charge free; determine the
charge delivered to and the power supplied by the source.
a) 0.01C, 0MW. b) 0.01C, 5W. c) 0.1C, 10MW. d) None of the above
9- Expression of energy storage by a capacitor is…….
𝑄𝑉 𝑄2 𝐶𝑉 2
a) b) c) d) All of the above
2 2𝐶 2

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10- An uncharged capacitor having a capacitance of 40 μF is connected across 250 V
DC source. The charging current will be least……
a) when capacitor is fully charged.
b) when capacitor is half charged.
c) when capacitor is almost 25% charged.
d) initially.
11-An uncharged capacitor and a 1 kΩ resistor are connected in series with a switch
and a 6 V battery. At the instant the switch is closed, the voltage across the
capacitor is ………….
a) 6 V b) 3 V c) 2 V d) 0 V
12-The capacitor will complete its discharge most rapidly in…….
a) 10 μF capacitor with a 10 V charge, discharging through a 1 kΩ resistor
b) 50 pF capacitor with a 20 mV charge discharging through a 200 milli-ohm
resistance
c) 10 μF capacitor with a 50 V charge discharging through a 1 kΩ resistor
d) Discharge rate will be same in all cases.
13-When a capacitance is connected to a DC voltage, the value of charging current is
……… at time t=RC if the initial current is 2A.
a) 0.74 A b) 1.26 A c) 0.5 A d) 2.89 A
14-An 8microF uncharged capacitor is connected in series with a 0.5 megaohm
resistor and a 200 V DC voltage supply. Calculate the time taken for the potential
difference across the capacitor to grow to 160V.
a) 6.93s b) 7.77s c) 3.22s d) None of the above
15-A charged capacitor with a 50V voltage is connected in series with a 0.5 ohm
resistor and a 200 V DC voltage supply. The initial value of capacitor current at
𝑡 = 0+ is…….
a) 300 A b) -400 A c) -100 A d) None of the above
16-A charged inductor of initial current 50A is connected in series with a 0.5 ohm
resistor and a 200 V DC voltage supply. The final value of inductor current at 𝑡 =
infinity is…
a) 100 A b) 30 A c) 400 A d) None of the above
17-A charged inductor of initial current 500A is connected in series with a 0.5 ohm
resistor and a 200 V DC voltage supply. The final value of inductor current at 𝑡 =
infinity is…
a) 400 A b) 100 A c) 600 A d) None of the above

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18-A charged inductor of initial current 500A is connected in series with a 0.5 ohm
resistor and a 200 V DC voltage supply. The initial value of inductor voltage at
𝑡 = 0+ is…
a) -50 V b) 200 V c) 250 d) None of the above
19- While charging, what happens to the inductor voltage?
a) Remains constant
b) Increases linearly
c) Decreases exponentially
d) Increases exponentially
20-When will be capacitors fully charged?
a) When the capacitor voltage is zero
b) When the supply voltage is equal to the capacitor voltage
c) When the capacitor voltage is infinity
d) None of the above
21-The switch in the circuit in Figure 1 has been closed for a long time. It is opened
at t = 0. The capacitor voltage 𝑣(𝑡) for t > 0 is ……..
t=0
300 Ω
Figure
Figure 14
+
100 Ω
50 V +
v(t) i0
_
2i0
0.1 F

a) 5𝑒 −3𝑡/10 V b) 10𝑒 −3𝑡/10 V c) 5(1 − 𝑒 −3𝑡/10 ) d) None of the above

Q 22-26: The switch in the circuit in Figure 2 has been closed for a long time. It is
opened at 𝑡 = 0.
t=0
10 μF
Figure 2 5
Figure
200 Ω
10 A i(t) 120 Ω
100 mH

3
22-When the switch is opened at t = 0, the resulting circuit is……
a) a source-free b) a source RLC c) a source d) a source-free RC
RLC circuit circuit RC circuit circuit
23-When the switch is opened at t = 0, the inductor current is……
a) -10 A b) 10 A c) 5 A d) -5 A
24-The total energy dissipated in the 120 Ω resistor after the switch is opened (t = 0+)
a) 5 J b) 10 J c) 15 J d) None of the above
25-What kind of the current response will it produce?
a) Under b) Over c) Critical d) Any of the above
damped damped damped
26-The current 𝑖(𝑡) for 𝑡 > 0 is ……..
𝑒 −600𝑡 (−10 𝑐𝑜𝑠( 800𝑡)) 𝑒 −600𝑡 (−10 + 7.5𝑡) −10 𝑒 −600𝑡 None of the above
−100𝑡
+ 7.5𝑒
Q 27-29: Consider the circuit in Figure 3. Assume the switch has been open for a
long time and is closed at 𝑡 = 0.

Figure 3

27-The initial capacitor voltage 𝑣(0) is ……

a) 2 V b) 3 V c) 4 V d) None of the above
28-The final capacitor voltage 𝑣(∞) is ……
a) 2.5 V b) 3.5 V c) 4.5 V d) None of the above
29-The capacitor voltage 𝑣(𝑡) for t > 0 is ……..
a) 1.5(3 − b) 1.5(1 − c) 1.5(3 − d) None of the above
−100𝑡/15 −100𝑡/15 −10𝑡
𝑒 )V 𝑒 )V 𝑒 )V
Q 30-32: In the circuit given in Figure 4, switches S1 and S2 are open for a long time.
When t=0 switch S1 is closed while switch S2 is kept open. After 10 seconds the
switch S2 is also closed.

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 Figure 4

30-The current flowing through the inductor 𝑖(𝑡) is ………for 𝑡 > 0

a) 5−5𝑒 −𝑡 𝐴 b) 5−5𝑒 −0.3𝑡 𝐴 c) −5𝑒 −0.3𝑡 𝐴 d) −5𝑒 −𝑡 𝐴
31-The voltage across the 4-Ω resistor is …..when 𝑡 = 2 seconds
a) 17 V b) 15 V c) 12 V d) None of the above
32-The voltage across the 4-Ω resistor is ….. when 𝑡 = 12 seconds.
a) 17 V b) 19 V c) 15 V d) None of the above
33-For the circuit shown in (a), the source voltage is given in (b). Find the current
𝑖𝐿 (t) if 𝑖𝐿 (0) = 1 A for 1 < 𝑡 < 2 𝑠𝑒𝑐.

a) 2𝑡 2 − 3𝑡 + 2 b) −2𝑡 2 + 3𝑡 c) −2𝑡 2 − 3𝑡 d) None of the above

34-A charged capacitor with a 50V voltage is connected in series with a 0.5 ohm
resistor and a 30 V DC voltage supply. The initial value of capacitor current at
𝑡 = 0+ is…….
a) 100 A b) -40 A c) 60 A d) None of the above

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35-A charged inductor of initial current 50A is connected in series with a 0.5 ohm
resistor and a 200 V DC voltage supply. The initial value of inductor voltage at
𝑡 = 0+ is…
a) 175 V b) -200 V c) 25 V d) None of the above

Please, Choose the correct answer by filling in the correct letter. Make sure that your
answer matches the question number and that the entire circle is filled.

1 14 27

2 15 28

3 16 29

4 17 30

5 18 31

6 19 32

7 20 33

8 21 34

9 22 35

10 23

11 24

12 25

13 26

With best wishes

Dr. Amir Abdelmenaem