Power magnitude comparison: Eighteen thousand watts corresponds to which standard SI-prefixed power unit?

Difficulty: Easy

Correct Answer: 18 kW

Explanation:


Introduction / Context:
Choosing the correct SI prefix clarifies scale when specifying generators, heaters, or loads. Converting 18,000 W into a concise form demonstrates mastery of kilo, mega, milli, and micro prefixes for power.


Given Data / Assumptions:

  • Given power: 18,000 W.
  • Prefixes: kilo (k) = 10^3, mega (M) = 10^6, milli (m) = 10^-3, micro (µ) = 10^-6.
  • Goal: select the appropriate prefixed unit.


Concept / Approach:
Divide by 10^3 to get kilowatts when the value is in the thousands. Only one option should reflect 18 × 10^3 W correctly as 18 kW.


Step-by-Step Solution:

Compute: 18,000 W / 1,000 = 18 kW.Check alternatives: 18,000 W / 10^6 = 0.018 MW (not offered); milli or micro would drastically reduce the value.Choose the exact matching text: '18 kW'.


Verification / Alternative check:
Reverse check: 18 kW * 1,000 = 18,000 W, confirming correctness precisely.


Why Other Options Are Wrong:

  • 18 mW: Equals 0.018 W; many orders too small.
  • 18 MW: Equals 18,000,000 W; three orders too large.
  • 18 µW: Equals 0.000018 W; absurdly small for the context.


Common Pitfalls:

  • Mistaking uppercase M (mega) for lowercase m (milli), which flips scale by 10^9.
  • Forgetting to convert back to watts to sanity-check the result.


Final Answer:
18 kW

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