asdas asked in 科學工程學 · 8 years ago

# 電路學名詞小問題?

As a design engineer, you are asked to design a lighting system consisting of a 70-W power supply and two lightbulbs as shown in Fig. 2.124. You must select the two bulbs from the following three available bulbs.

R1 = 80Ω, cost = \$0.60 (standard size)

R2 = 90Ω, cost = \$0.90 (standard size)

R3 = 100 Ω, cost = \$0.75 (nonstandard size)

The system should be designed for minimum cost such that I = 1.2 A ± 5 percent.

R1 = 80Ω, cost = \$0.60 (standard size)

R2 = 90Ω, cost = \$0.90 (standard size)

R3 = 100 Ω, cost = \$0.75 (nonstandard size)

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• 麻辣
Lv 7
8 years ago

As a design engineer, you are asked to design a lighting system consisting of a 70-W power supply and two lightbulbs as shown in Fig. 2.124. You must select the two bulbs from the following three available bulbs.

R1 = 80Ω, cost = \$0.60 (standard size)

R2 = 90Ω, cost = \$0.90 (standard size)

R3 = 100 Ω, cost = \$0.75 (nonstandard size)

The system should be designed for minimum cost such that I = 1.2 A ± 5 percent. 以上為原題目.我想問的問題是

R1 = 80Ω, cost = \$0.60 (standard size)

R2 = 90Ω, cost = \$0.90 (standard size)

R3 = 100 Ω, cost = \$0.75 (nonstandard size)

的standard size和nonstandard size對做題目時有啥影響?

ans: 沒有影響.目標=最便宜

w=I^2*R=1.2^2*80=115.2Watts

非常接近70watts

所以選用80Ω最便宜

• Anonymous
7 years ago

我每次都是去這里看的哦, http://lvmiss.com/

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