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S302 20/08/
TH E MANCH ESTER M ETR O PO LITAN UNIVER SITY
FACULTY O F SCIENCE AND ENGINEER ING
D EPA R TMENT O F ENGINEER ING AND TECH NO LO GY
SESSIO N 2001/
Exam ination for th e H ND ELECTR O NIC ENGINEER ING YEA R O NE
UNIT 64EE1201 : ELECTR ICALENGINEER ING SCIENCE I
Tuesday 21 May 2002
9 .30 am to 11.30 am
Instructions to Candidates
A ttem pt allquestions. A ssessm ent w illb e b ased on th e m ark s ob tained from your b e st tw o attem pts.
Break dow n of m ark s for each question is sh ow n in square parenth eses.
continued
All questions carry equal marks.
- In th e circuit of Figure Q 1, w h ich initially h as no current, th e sw itch is closed at tim e t = 0. Calculate:- (a) th e circuit tim e constant w h en th e sw itch is closed. [2] (b ) th e current i 2 w h en th e sw itch h as b e e n closed for 1 second. [2] (c) th e current i 2 4 m s after th e sw itch w as closed. [4] (d) th e voltages vL, and vR 2 4 m s after th e sw itch w as closed. [4] (e) th e tim e tak en for th e supply current, is to reach 500m A [5]
Th e sw itch is k ept closed for 1 second and th en opened. Calculate:- (f) th e circuit tim e constant w h en th e sw itch is open [2] (g) th e current, i 2 , im m ediately after opening th e sw itch [2] (h ) th e voltage vR 1 and its direction im m ediately after opening th e sw itch. [4]
You m ay assum e th at th e equations relating th e grow th and decay of current in a series connected resistor and inductor are:
w h ere th e sym b ols h ave th eir usualm eanings
Figure Q 1
i = I (1o − e ) i = I (^) oe
− Rt − L
Rt and L
t=
G (^) 600mH
i
=30V vL
vR
R 2 = 90 Ω 2
is
R 1
i 1
vR
Vs
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- State and explain (a) Th e Maxim um Pow er Transfer Th eorem and [4] (b ) Th evenin's Th eorem. [4]
For th e circuit of Figure Q 3, it is required th at m axim um pow er is transferred from th e source to th e load im pedance Z. A llstated im pedances are for a frequency of 1 k H z.
Calculate (c) th e com ponent values of Z for m axim um pow er dissipation in Z and [12] (d) th e value of th is m axim um pow er dissipation. [5]
Figure Q 3
END
G (4+j3)Ω Z
(5+j12) 25/0^0 Ω 1kHz
