Conservation Principles Check

1. The first law of thermodynamics, restated as a balance, says:
Energy is conserved only within closed systems that have no flows crossing the boundaryEnergy always degrades to heat before it can leave any systemEvery unit of energy entering a system must leave it, or still be insideEnergy can be created inside a system if enough power is supplied
2. Why must you define a system boundary before building a balance?
Boundaries are strictly needed for mass balances but are optional for energy balancesIt is a documentation formality with no effect on the numbersThe boundary decides which streams count, so it sets the question you answerOnly fully closed systems can be given a meaningful boundary
3. A boiler running at a constant load, hour after hour, is best approximated as:
A transient systemAn adiabatic systemA steady-state systemA closed system
4. You measure a motor's electrical input and mechanical output, and estimate its heat loss separately. The three don't quite add up. What does that gap most likely indicate?
The instruments disagree, so the whole exercise should be discardedA stream crossing the boundary hasn't been measured or counted yetNormal behaviour, since balances never close on real equipmentThe first law does not hold exactly for rotating machinery
5. For a steady-state open system, the general balance equation 'Accumulation = In − Out' simplifies to:
In = OutOut = 0In × Out = 1In = 0

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