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Unformatted text preview: ECE210 - Fall 2010 - Homework 02 Solutions 1. Your non-ECE friend finds many strands of decorative (Christmas tree) lights, and decides to use them to decorate for a party hes hosting. Each strand has 50 bulbs in series, and you measure with an ohmmeter and find that each bulb has a resistance of 2 . (a) If your friend hooks up the strands as shown in Figure 1 determine V x , i x , i 1 , and i 2 . +- 120 V V x 1 strand 1 strand i 1 i 2 i x Figure 1: Figure only for problem 1(a). Sol: First we get the resistance of a strand: R strand = 50 2 = 100 . Equivalent resistance of two equal strands in parallel: R strand k R strand = R strand R strand R strand + R strand = R strand 2 = 50 . Using a voltage divider: V x = 120 V R strand k R strand R strand k R strand + R strand = 120 V 50 50 +100 = 40 V . Ohms law: i x = 120 V R strand k R strand + R strand = 120 V 150 = 4 5 A = 0 . 8 A . Since in this case the strands have equal resistance: i 1 = i 2 = i x 2 = 0 . 4 A ....
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This note was uploaded on 03/05/2011 for the course ECE 210 taught by Professor Staff during the Fall '08 term at University of Illinois, Urbana Champaign.
- Fall '08