Practice Problems

Problem 1

Convert the following numbers to engineering notation:

• 46500000 V

• 0.00000983 A

• 792000000000 Ω

• 6150 V, 0.0019 A

• 20000000000 Ω

Problem 2

Use the decision matrix below to determine which laptop would be the best choice.

	Screen Size	Cost
Laptop A	15	$1000
Laptop B	17	$1200

Decision matrix:

Laptop	Screen Size			Cost			Total
Weight
	Value	Norm	Weighted	Value	Norm	Weighted
A
B

Problem 3

Determine which house would be the best choice.

	Commute Time	Square Footage	Cost
House A	15 min	2000	$220000
House B	5 min	1500	$250000
House C	30 min	3000	$200000

Decision matrix:

House	Commute Time			Square Footage			Cost			Total
Weight	Determined in Class			Determined in Class			Determined in Class
	Value	Norm	Weighted	Value	Norm	Weighted	Value	Norm	Weighted
A	15	0.333		2000	0.667		$220K	0.909
B	5	1.000		1500	0.500		$250K	0.800
C	30	0.167		3000	1.000		$200K	1.000

Problem 4

You are evaluating three different AC-to-DC converters that all meet your requirements for ripple and cost. Since you want to use these devices for a scientific instrument, you really want to minimize ripple but are limited by a small budget. Use a decision matrix to choose the best one. Assume a weight of 60% for ripple and 40% for cost.

Part	Ripple	Cost
A	30 mV	$20
B	35 mV	$14
C	45 mV	$12

Decision matrix:

Part	Ripple			Cost			Total
Weight
	Value	Norm	Weighted	Value	Norm	Weighted
A
B
C

Problem 5

Three options are proposed to provide power to a new community. The cost and efficiency for each option are shown below.

Option	Cost	Efficiency
X	$3.2M	99.4%
Y	$3.0M	97.2%
Z	$2.8M	86.0%

(a) If cost and efficiency are considered equally as important, which is the better option?

Option	Cost			Efficiency			Total
Weight
	Value	Norm	Weighted	Value	Norm	Weighted
X
Y
Z

(b) If efficiency is considered 9 times as important as cost, which is the better option?

Option	Cost			Efficiency			Total
Weight
	Value	Norm	Weighted	Value	Norm	Weighted
X
Y
Z

Problem 6

Convert the following into engineering notation:

(a) 5.45 × 10⁻⁷ A
(b) 123,400 W
(c) 8.33 × 10⁷ V
(d) 4.3 × 10¹⁰ bits (b)
(e) 1,497,000 Hz
(f) 76.2 × 10⁻⁴ m
(g) 2.31 × 10⁻⁵ m
(h) 1.78 × 10⁻¹⁴ W