Unit conversion of power: Convert 0.025 W into an equivalent expression using standard metric submultiples.
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A25 mW
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B2,500 µW
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C0.00025 mW
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D25 kW
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E250 µW
Answer
Correct Answer: 25 mW
Explanation
Introduction / Context:Engineering problems frequently require converting between watts and submultiples such as milliwatts and microwatts. Mastering metric prefixes avoids scale errors and enables quick interpretation of specifications for sensors, amplifiers, and power supplies.
Given Data / Assumptions:
- Given power P = 0.025 W.
- Metric prefixes: 1 mW = 10^-3 W and 1 µW = 10^-6 W.
- We want an exactly equivalent, properly scaled expression.
Concept / Approach:
Use unit equivalences and multiply/divide by powers of ten. Converting watts to milliwatts requires multiplying by 10^3. Converting watts to microwatts requires multiplying by 10^6.
Step-by-Step Solution:
Convert to milliwatts: 0.025 W * 10^3 = 25 mW.Check as microwatts: 0.025 W * 10^6 = 25,000 µW.Compare to options: 25 mW matches exactly; 2,500 µW equals 0.0025 W (too small).Therefore, the correct equivalent is 25 mW.Verification / Alternative check:
Reverse conversion: 25 mW / 1000 = 0.025 W. This confirms the accuracy.
Why Other Options Are Wrong:
2,500 µW = 2.5 mW = 0.0025 W (ten times smaller). 0.00025 mW = 2.5 * 10^-7 W (far smaller). 25 kW is 25,000 W (enormously larger). 250 µW = 0.00025 W (much smaller).
Common Pitfalls:
Misplacing decimal points, confusing mW with µW, and forgetting that k (kilo) is 10^3 while m (milli) is 10^-3.
Final Answer:
25 mW