Expressing electric current with SI prefixes: Fourteen milliamperes equals which of the following standard current notations?
Electronics
Quantities and Units
Difficulty: Easy
Choose an option
-
A14 MA
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B14 µA
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C14 kA
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D14 mA
Answer
Correct Answer: 14 mA
Explanation
Introduction / Context:Smoothly reading and writing SI-prefixed quantities avoids mistakes in circuit design and documentation. This question checks recognition of the correct unit symbol for a given magnitude of current.
Given Data / Assumptions:
- Quantity: fourteen milliamperes.
- SI prefixes: micro (µ) = 10^-6, milli (m) = 10^-3, kilo (k) = 10^3, mega (M) = 10^6.
- Base unit: ampere (A).
Concept / Approach:Map the word 'milli' to its symbol and power of ten. The textual magnitude already states milliamperes, so we simply choose the matching symbolized form rather than converting to a different scale.
Step-by-Step Solution:
Interpretation: 'fourteen milliamperes' = 14 milliamperes.Prefix mapping: milli → symbol 'm' → 10^-3.Write compactly: 14 mA.Verification / Alternative check:Convert to amperes then back: 14 mA = 14 * 10^-3 A. Re-expressing with the milli prefix returns 14 mA, confirming the choice.
Why Other Options Are Wrong:
- 14 MA: Megaampere equals 14 * 10^6 A, astronomically larger.
- 14 µA: Microampere equals 14 * 10^-6 A, much smaller.
- 14 kA: Kiloampere equals 14 * 10^3 A, far larger.
Common Pitfalls:
- Confusing uppercase M (mega) with lowercase m (milli).
- Misreading µA (micro) as mA (milli) due to font or display issues.
Final Answer:14 mA