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UNIVERSITY OF MASSACHUSETTS DARTMOUTH COLLEGE OF ENGINEERING EGR 101 INTRODUCTION TO ENGINEERING I This assignment is due Thursday, October 18, 2012. Use engineering papers. Show all of your steps. Present your work neatly and clearly. Box your final answers. Problem 1: Consider the following circuit that consists of multiple series-aiding and series-opposing batteries, which power a resistance of 10k . Indicate whether point A is at higher or lower potential than point B, and explain why. adding series aided batteries going from A to B = -9 +3 +1.5 +1.5 +6 -9 +1.5 +1.5+1.5 = -1.5 V Therefore A is at a higher potential Reduce the circuit to a single battery with a net voltage equivalent to the algebraic sum of all the voltages in the original circuit. o Show the proper polarity of the battery at points A and B; and o indicate which way the conventional current flows. A+ and B- and the current flows CCW Calculate the current in mA. I = V/R = 1.5 V/ 10 kΩ = 0.15 mA = 150 µA CCW Calculate the power provided by the battery in mW. P = VI = 1.5 V* 150 µA = 225 µW Problem 2: Problem 25 pg 94. Output power of the source = V*I = 24V*8A = 192 W 80% of max power = 0.8*192W = 153.6 W N x 5W = 153.6 W N = 30.72 or a maximum of 30 lights Problem 3: Problem 13 pg 93. Use information in section 2.3.5 on pg 56 in text I = 6V/120Ω = 0.05 A power dissipated by resistor = I2R = 0.3W this is > 1/8 and 1/4 Watt, so next large resistor is 1/2 W. Problem 4: Problems 6b, d, f on p. 73 strictly by the resistor color code as shown in Figure 2.10 on p. 52. b. Orange Blue Silver = 30 x 0.1 = 3.0Ω d. White Black Green = 98 x 105 = 9.8 M Ω f. Brown Gray Silver = 18 x 0.1 = 1.8 Ω Problem 5: Problems 8b, e, g on p. 74 strictly by the resistor color code as shown in Figure 2.10 on p. 52. e. 20 MΩ = Red Black Blue g. 160kΩ = Brown Blue Yellow g. 9.1MΩ = White brown Green Problem 6: Complete the chart in problem 21 on p. 94. Current 10 mA 0.5 mA 8.4 mA 15 mA 24 mA Voltage 400 V 32 V 27.6 V 45 V 288 V Resistance 40 kΩ 64 kΩ 3.3 kΩ 3.0 kΩ 1.2 kΩ Power 4W 16 mW 231 mW 675 mW 6.9 W