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Unformatted text preview: FEB12QDOé 15:06 Simone P.01/01 University of Toronto ECE 159S  Electrical Fundamentals February 12th 2004 Last Name: First Name: Student Number: Quiz 2 — Electric Currents and Magnetic Field (6 = 1.6x10‘19 C, so = 8.85x10'12 C2/Nm2, p0 = 41rx10'7 Tm/A) Question I [5 marks]
A 10 £2 resistor made of an unknown material is rated for 1/10 Watt operation. (a) What are the maximum current and the maximum voltage that the resistor can withstand
before failing? (2 marks) (b) If the resistor fails within 1 us, what energy is required? (I mark) (c) The resistor measures 1 mm x 1 mm x 1 cm with current ﬂow in the longer dimension. What
is the resistivity of this material? (I mark) ((1) What is the current density just before failing? (1 mark) 0») F: VI VIIK :7 ?=IZR =_V._ :0.) A lrmek P= 0.1 w Ver= t/PR = \lmxzo = l \/ mack t) _. ~ 
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.6 (0 mm lof2 TOTAL P.01 FEB122004 14:39 erik P.01/01 University of Toronto ECE 159S  Electrical Fundamentals February 12th 2004 Question 2 [5 marks]
Four straight, inﬁnitely long conductors with currents I, I, 21 and 11 are arranged as shown in
the ﬁgure below (I, I, 21 in the corners of an equilateral triangle and 11 in its center). I
g; down (a) Obtain the net force/meter (magnitude and direction) that is applied to the conductor
located at the center. Draw the vector on the ﬁgure. (3 marks) (b) Assume a mass density of M (kg/m) for the conductor at the center. Obtain the current 11,
in terms of the other parameters, such that the conductor is levitating. (2 marks) (Hint: The magnitude of the force per unite length for two long conductors carrying currents
11 and 12 is lF= no 11 12/ (27rd), where d is the distance between the two conductors.) (a) ' __, .= “911‘
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ﬁat: Zlﬁlcosma'  = 2x ZRJ x3  Nd J 2‘ 217:1, J
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Lb) 'FMt—HgJzo —>— 2% JN8J—O
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Q .5: 2_ 2nd 8 20f2 TOTAL P . 01 ...
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 Winter '08
 B.wang
 Toronto ECE 159S, University of Toronto ECE

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