UNIVERSITY OF MASSACHUSETTS DARTMOUTH
COLLEGE OF ENGINEERING
EGR 101 INTRODUCTION TO ENGINEERING I
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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