Examination Copyright reserved. Eksamen Kopiereg voorbehou. Module EBN122 Elektrisiteit en Elektronika 13 November 2009

Transcription

1 Departement Elektriese, Elektroniese en Rekenaar-Ingenieurswese Eksamen Kopiereg voorbehou Module EBN Elektrisiteit en Elektronika 3 November 009 Department of Electrical, Electronic and Computer Engineering Examination Copyright reserved Module EBN Electricity and Electronics 3 November 009 Eksamensinligting: Exam information: Maksimum punte: Maximum marks: Duur van vraestel: Duration of paper: minute 80 minutes Totale aantal bladsye (hierdie blad ingesluit): Total numer of pages (including this page): Volpunte: Full marks: Oopboek / toeboek: Open / closed book: Toe Closed BELANGRIK- IMPORTANT. Die eksamenregulasies van die Universiteit van Pretoria geld. The examination regulations of the University of Pretoria apply.. Alle vrae moet op die ANTWOORDBLAD beantwoord word. All Questions must be answered on the ANSWER SHEET. 3. Studente mag hul eie rowwe berekeninge op die vraestel doen die vraestel word nie ingeneem nie. Students may do their own rough calculations on the question paper the question paper will not be taken in. 4. Polêre vorm: θ Polar form: A ; Reghoekige vorm: a + jb A θ ; Rectangular form: a + jb J Joubert Dosent(e): D Bhatt Lecturer(s): 3 B Mabuza Groephoof: Ek bevestig dat die vraestel die uitkomstes toets soos gespesifiseer in die studiehandleiding. Group head: I confirm that the question paper evaluates the outcomes as specified in the study guide. Groephoof: Group Head: Prof J Joubert Handtekening: Signature: EBN-009-Exam

2 VRAAG/QUESTION [] Vraag. Question. Fig.. Bepaal die spannings v, v, en die stroom i. [3] Determine the voltages v, v and the current i. [3] EBN-009-Exam

3 Vraag. Question. Bereken die totale lading deur 'n toestel by t = s, as die stroom deur die toestel gegee word deur die uitdrukking: i(t) = 5 ( - e -t ) ma. [] Calculate the total charge through a device at t = s, when the current through the device is given by the expression: i(t) = 5 ( - e -t ) ma. [] EBN-009-Exam 3

4 Vraag.3 Question.3 Fig..3 Bereken Io, en Vo? [] Calculate Io, and Vo? [] EBN-009-Exam 4

5 Vraag.4 Question.4 Fig..4 Bereken die volgende: [3] (a) i (b) v en (c) die drywing ge-assosieer met die 30A stroombron? Calculate the following: [3] (a) i (b) v and (c) the power associated with 30A current source? EBN-009-Exam 5

6 Vraag.5 Question.5 + Vx - R R 40V 0V 3R - 8V + 0.8m W Fig..5 Bereken: (a) R [] (b) V x [] Calculate: (a) R [] (b) V x [] EBN-009-Exam 6

7 Vraag.6 Question.6 Fig..6 Bepaal [] (a) G eq as G = 0 (b) G eq as G = Determine [] (a) G eq when G = 0 (b) G eq when G = EBN-009-Exam 7

8 Vraag.7 Question.7 Fig..7 Bereken R eq [] Calculate R eq [] EBN-009-Exam 8

9 Vraag.8 Question.8 Fig..8 Calculate R eq [] Calculate R eq [] EBN-009-Exam 9

10 Vraag.9 Question.9 Fig..9 (a) Bepaal V ab en I? [] (b) As die 5V bron afgeskakel sou word, wat is die weerstand oor terminale a-b? [] (a) Determine V ab and I? [] (b) If 5V source voltage is switched off what is the resistance across terminals a-b? [] EBN-009-Exam 0

11 VRAAG/QUESTION [4] Vraag. Question. Fig.. Gebruik node-analise en bereken v o [] Using nodal analysis calculate v o [] EBN-009-Exam

12 EBN-009-Exam Vraag. Question. Bepaal die determinant en los die matriksvergelyking op om v te bepaal. [] = v v v Find the determinant and solve the matrix equation to find v. [] = v v v

13 Vraag.3 Question.3 Fig..3 Gebruik node-analise om die stroombaan op te los. Bepaal v 0 en v [3] Use nodal analysis to solve the circuit and find the values of v 0 and v [3] EBN-009-Exam 3

14 Vraag.4 Question.4 Fig..4 β = 0 en v BE = 0.75V vir die bostaande stroombaan. (a) Bepaal I s as v o = 5.5V, en skryf jou antwoord in µa. [] (b) Bepaal v CE as v o = 4.5V. [] β = 0 and v BE = 0.75V for the circuit above. (a) Determine I s if v o = 5.5V, and express your answer in µa. [] (b) Determine v CE if v o = 4.5V. [] EBN-009-Exam 4

15 Vraag.5 Question.5 Fig..5 (a) Bereken stroom i o in die stroombaan [] (b) Wat sal die waarde van i o wees as die spanningsbron na 0V verander word [] (a) Calculate current i o in the circuit [] (b) What will the value of this current i o be when the source voltage is raised to 0V [] EBN-009-Exam 5

16 Vraag.6 Question.6 Fig..6 Bepaal die waarde van n weerstand wat jy oor terminale a-b kan plaas sodat maksimum drywing na die weerstand oorgedra word. [] Determine the value of a resistor placed across the open terminals, a-b, resulting in maximum power transferred to the resistor. [] EBN-009-Exam 6

17 Vraag.7 Question.7 Fig..7 Gebruik brontransformasies om v o te bepaal [3] Use source transformation to find v o [3] EBN-009-Exam 7

18 Vraag.8 Question.8 Fig..8 Bepaal R th and V TH met verwysing tot terminale a b. [] Find R th and V TH with respect to terminals a b. [] EBN-009-Exam 8

19 Vraag.9 Question.9 Fig..9 Bepaal V TH met verwysing tot terminale a b. [] (verwyder die 5Ω las) Find V TH with respect to terminals a b. [] (remove the 5Ω load) EBN-009-Exam 9

20 Vraag.0 Question.0 Fig..0 Bepaal die Thevenin-ekwivalente weerstand R TH met verwysing tot terminale a-b. [] Determine the Thevenin equivalent resistance R TH with respect to terminals a-b. [] EBN-009-Exam 0

21 VRAAG 3 QUESTION 3 [0] Vraag 3. Question 3..kΩ 50Ω 0Ω ma 50Ω + V 0-300mV + - 0Ω + V - Fig. 3.(a) Fig. 3.(b) (a) Bepaal V 0 in Fig. 3.(a) [] (b) Bepaal V in Fig. 3.(b) [] (a) Determine V 0 in Fig. 3.(a) [] (b) Determine V in Fig. 3.(b) [] EBN-009-Exam

22 Vraag 3. Question 3. 80Ω 0Ω V + - i + 0Ω V - Fig. 3. (a) Bepaal V in Fig. 3. [] (b) Bepaal i in Fig. 3. [] (a) Determine V in Fig. 3. [] (b) Determine i in Fig. 3. [] EBN-009-Exam

23 Vraag 3.3 Question Ω 00Ω 50Ω 6V Ω + V 3-00Ω 50Ω 00Ω + V 4 - Fig. 3.3 (a) Bepaal V 3 in Fig. 3.3 [] (b) Bepaal V 4 in Fig. 3.3 [] (a) Determine V 3 in Fig. 3.3 [] (b) Determine V 4 in Fig. 3.3 [] EBN-009-Exam 3

24 Vraag 3.4 Question 3.4 (a) Die stroom deur 'n mf kapasitor is 7sin(t) ma vir t 0 s. Bepaal die spanning oor die kapasitor by t = 0. s. Aanvaar v(0) = 0 V. [] (b) Die stroom deur 'n 0 mh induktor is 4e -6t ma vir t 0 s. Bepaal die spanning v(t) oor die induktor. [] (a) The current through a mf capacitor is 7sin(t) ma for t 0 s. Determine the voltage across the capacitor at t = 0. s. Assume v(0) = 0 V. [] (b) The current through a 0 mh inductor is 4e -6t ma for t 0 s. Determine the voltage v(t) across the inductor. [] EBN-009-Exam 4

25 Vraag 3.5 Question 3.5 0Ω A 0Ω 0µF 50Ω 40Ω 5H Fig. 3.5 Bepaal W L en W C, die energie gestoor in die induktor en kapasitor onderskeidelik. [4] Determine W L and W C, the energy stored in the inductor and capacitor respectively. [4] EBN-009-Exam 5

26 VRAAG 4 QUESTION 4 [4] Vraag 4. Question 4. (a) Skryf as n enkele cosinus uitdrukking: v(t) = 4.4cos(ωt + 45 ) + 0cos(ωt - 90 ) V [] (a) Write as a single cosine expression: v(t) = 4.4cos(ωt + 45 ) + 0cos(ωt -90 ) V [] (b) Watter van die volgende fasors loop voor? V = 0 30, V = 5 0 [] (b) Which of the following phasors is leading? V = 0 30, V = 5 0 [] (c) Bepaal V (in reghoekige vorm): + j V j V = 0 [] (c) Determine V (in rectangular form): + j V j V = 0 [] EBN-009-Exam 6

27 Vraag 4. Question 4. (a) Evalueer die volgende (skryf antwoord in reghoekige vorm): (a) Evaluate the following (write the answer in rectangular form): ( 0 + j0) ( 0 + j0) [] 3 + j4 3 + j4 [] ( ) ( ) (b) Evalueer die volgende (skryf antwoord in polêre vorm): ( 4 j9) o j30 + e [] ( + j8) (b) Evaluate the following (write the answer in polar form): ( 4 j9) o j30 + e [] ( + j8) EBN-009-Exam 7

28 Vraag 4.3 Question A jω 6Ω 5Ω I I V j5ω Gebruik lus-analise om twee gelyktydige vergelykings vir fasors I en I op te stel. Skryf in die vorm ai di + bi + ei = c met a, b, c, d, e en f komplekse koeffisiënte in reghoekige vorm. [4] = f Use mesh analysis to set up two simultaneous equations for phasors I and I. Write in the form ai di + bi + ei = c with a, b, c, d, e and f complex coefficients in rectangular form. [4] = f EBN-009-Exam 8

29 Vraag 4.4 Question 4.4 (t) v s 5Ω 3Ω i(t) mf 5mH v(t) i s (t) _ Gebruik die beginsel van superposisie: (a) Bereken i(t) slegs agv die spanningsbron o v s ( t) = 0cos(00t + 30 ) [] (b) Bereken v(t) slegs agv die spanningsbron o v s ( t) = 0cos(00t + 30 ) [] (c) Bereken i(t) slegs agv die stroombron i s ( t) = 5cos(00t) [] Use the principle of superposition: (a) Determine i(t) only due to the voltage source o v s ( t) = 0cos(00t + 30 ) [] (b) Determine v(t) only due to the voltage source o v s ( t) = 0cos(00t + 30 ) [] (c) Determine i(t) only due to the current source i s ( t) = 5cos(00t) [] EBN-009-Exam 9

30 Vraag 4.5 Question 4.5 8Ω j5ω a 4 0 V + - j0ω b Bepaal die Norton ekwivalent tov terminale a-b. Skryf die antwoorde in polêre vorm. [4] Find the Norton equivalent wrt terminals a-b. Write the answers in polar form. [4] EINDE - END EBN-009-Exam 30

31 EBN EKSAMEN ANTWOORDBLAD/ EXAM ANSWER SHEET 3 NOVEMBER 009 Van en voorletters: Surname and initials: Graadkursus: Degree Course: Tel. nr.: Tel no.: Student se besonderhede/student's details Studentenommer: Student number: PUNTE/MARKS Q / Q /4 Q3 /0 Q4 /4 Final /90 VRAAG /QUESTION [] VRAAG /QUESTION [4]. v = v = i =. v o =. Q =. = v =.3 I o = V o =.3 v o = v =.4 i = v = P =.4 I s = V CE =.5 R = V x =.5 i o = i o =.6 G eq = G eq =.6 R ab =.7 R eq =.7 v o =.8 R eq =.8 R TH = V TH =.9 V ab = I = R ab =.9 V TH =.0 R TH = EBN-009-Exam

32 VRAAG 3 QUESTION 3 [0] 3. (a) V 0 = (b) V = 3. (a) V = (b) i = 3.3 (a) V 3 = (b) V 4 = 3.4 (a) v(0.s) = (b) v(t) = 3.5 W L = W C = (a) v(t) = VRAAG 4 QUESTION 4 [4] 4. (b) (c) V = (a) (b) a = b = c = d = e = f = (a) i(t) = 4.4 (b) v(t) = (c) i(t) = 4.5 I N = Z N = EBN-009-Exam