Family Name Other Names Global ID Date
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Diplomas
Electrical and Telecommunications Engineering
EE1111
Question
Possible Marks
Actual Marks
1
30
2
30
3
40
Total
100
Mid-Semester Exam Reading time: 10 minutes Working time: 100 minutes Intake/Year: Term 1 2020
UNSW Diplomas
UNSW Global Pty Limited
UNSW Sydney NSW 2052 Australia
Copyright 2020
All rights reserved. Except under the conditions described in the Copyright Act 1968 of Australia and subsequent amendments, this publication may not be reproduced, in part or whole, without the permission of the copyright owner.
Directions to Candidates
This paper contains 8 pages.
Candidates must ATTEMPT ALL questions.
Answer each question in a separate answer booklet.
Marks for each question are indicated beside the question.
This paper MAY NOT be retained by the candidate.
Print the question number on the front page of each answer book. Authorised examination materials:
Candidates should use their own UNSW-approved electronic calculators.
This is a closed book examination.
Assumptions made in answering the questions should be stated explicitly.
All answers must be written in ink. Except where they are expressly required, pencils may only be used for drawing, sketching or graphical work.
For the numerical solutions, you can use either fraction form or floating-point form (maximum 2 digits after decimal point is enough)
QUESTION 1 [30 marks]
(i) [15 marks] For the circuit shown in Figure 1:
a. (12marks)Calculatetheequivalentresistance. b. (3 marks) Find current io.
38 V
io
Req
Figure 1
(ii) [15 marks] Apply nodal analysis to find 𝑉0 and 𝑉𝑥 in the circuit of Figure 2. (Use the given current directions in the circuit in deriving your nodal equations).
6Io
+-
10V1 12
+
8A vx
–
V2
1
Io 2
– vo +
20 V
4
Figure 2
QUESTION 2 [30 marks]
(i) [15 marks] For the circuit shown in Figure 3:
a. (7 marks) Apply mesh analysis and show that mesh equations are given as below (Use the given current directions in the circuit in deriving your mesh equations):
6𝑖1 +4𝑖2 −5𝑖3 =−12 { −𝑖1 − 4𝑖2 + 7𝑖3 = −6
𝑖2 = 𝑖1 + 3
b. (2 marks) Given the values of mesh currents as i1 = -3.067 A, i2 = 0.067 A and
i3 = -1.333 A, find 𝑖0.
c. (6 marks) Given the values of mesh currents as i1 = -3.067 A, i2 = 0.067 A and
i3 = -1.333 A, calculate the power supplied/absorbed by each source. 6V
2
4 1
i2
i3 io
12 V
5 i13A
Figure 3
(ii) [15 marks] Use source transformation to find the voltage Vo in the circuit of Figure 4.
53
28A
+
2vo 15V
–
12
Figure 4
QUESTION 3 [40 marks]
(i)
[15 marks] For the circuit in Figure 5:
a. (5marks)Whatresistorconnectedacrossterminalsa-bwillabsorbmaximum
power from the circuit?
b. (10 marks) Calculate the maximum power that the obtained resistor in part (a) will absorb?
3A
(ii)
[25 marks] In the circuit of Figure 6, the switch has been in the open position for a long time before closing at time 𝑡 = 0.
a. (20marks)Giveanexpressionforthecapacitorvoltage𝑣𝑐(𝑡)(i.e.,asafunction of time) for all time.
b. (5 marks) Give an expression for the current of the 3-Ω resistor 𝑖𝑅3(𝑡) for 𝑡 > 0. 3
10 10
24 V
16
a
5R b
Figure 5
12 V
t=0 2 A 4 2F
+vc –
Figure 6
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