Conservation Principles Check

1. The first law of thermodynamics, restated as a balance, says:
Energy can be created if enough power is suppliedEvery unit of energy crossing into a system must leave it, or still be inside itEnergy always increases over time as equipment agesOnly mass is conserved; energy is not
2. Why must you define a system boundary before building a balance?
It's a formality with no effect on the numbersThe boundary you choose determines which streams are 'inside' and which are ignored, so it changes what question the balance actually answersBoundaries are only needed for mass balances, not energy balancesOnly closed systems need a boundary
3. A boiler running at a constant load, hour after hour, is best approximated as:
A closed systemA transient systemA steady-state systemAn unbalanced 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 — there's a small unexplained gap. What does that gap most likely indicate?
The first law has been violatedA stream crossing the boundary hasn't been fully measured or accounted for yetThe units must be wrong somewhere and the whole calculation should be discardedBalances never close in practice, so the gap can be ignored
5. For a steady-state open system, the general balance equation 'Accumulation = In − Out' simplifies to:
In = 0Out = 0In = OutAccumulation = In × Out

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