### Exam: Energy Conversions

Exam Number: 700697RR

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Question 3 of 20:

Why can the efficiency of a machine never be 100 percent?

A. Energy isn't conserved.

B. Machines can't transform energy from one type to another.

C. Friction converts some energy into a useless form.

D. The power used can't be measured accurately.

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The efficiency of a machine can never be 100 percent due to energy loss to less usable forms like heat, caused by factors such as friction. This leads to a reduction in overall efficiency in real machines below 100 percent.

Explanation:

The efficiency of a machine can never be 100 percent because some energy is always converted into a less useful form, such as heat, due to factors like friction and air resistance.

This loss of energy to unusable forms reduces the overall efficiency of the machine, making it impossible to reach 100% efficiency.

Efficiency in real machines will always be less than 100 percent due to work converted into unavailable heat, which is a common challenge faced in energy conversions.

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