Practice Problems

1. Convert the following numbers to engineering notation:

   • 46500000 V

   • 0.00000983 A

   • 792000000000 Ω

   • 6150 V, 0.0019 A

   • 20000000000 Ω

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

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

4. You are evaluating three different AC-to-DC converters that all meet your requirements for ripple (how much the supposed DC output actually changes) 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

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

6. Convert the following into engineering notation:

   (a) 5.45 × 10^-7 A
   (b) 123,400 W
   (c) 8.33 × 10^7 V
   (d) 4.3 × 10^10 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