22A

YOUR ANSWER: 93.25 percent.

You are correct.

Now, let's see how we could solve for the input power, if the efficiency and output were

known.

First, we will use the correct formula:

Efficiency = output x 100.

input

Now, suppose that we had a 5-horsepower motor operating at 74.6 per cent efficiency.

a. Put into formula known values:

74.6 = 5 x 746 x 100.

input

b. Multiply both sides of the equation by "input":

Input x 74.6 = 5 x 746 x 100 x input

input

c. Then, we have

input x 74.6 = 3730 x 100 = 373,000

input = 373,000 = 5,000 watts.

74.6

Now, you solve one.

A 4-horsepower motor operates at 80 percent efficiency; what is the input power?

3730 watts.

frame 26A

373 watts.

frame 21A

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IT0348

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