In basic energy accounting, what is the relationship between input energy and output energy in an ideal machine?

• A. Input energy equals output energy; there are no losses.
• B. Input energy is greater than output energy.
• C. Output energy exceeds input energy due to gains.
• D. They are unrelated.

Answer: (A)

In basic energy accounting, energy cannot be created or destroyed, so in an ideal machine all input energy is transferred to the output without any losses. That means the input energy equals the output energy, giving 100% efficiency. In real systems there are losses from friction, heat, and other dissipation, so input energy is greater than output energy; nothing should produce more energy than it consumes. The idea isn’t that output is unrelated to input—the two are directly tied by energy conservation, which the ideal model assumes.