Compute magnetomotive force (MMF) from turns and current For a coil with N = 150 turns carrying current I = 2 A, what is the magnetomotive force F = N * I (in ampere-turns)?
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A13.33 mAt
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B300 At
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C75 At
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D152 At
Answer
Correct Answer: 300 At
Explanation
Introduction / Context:Magnetomotive force (MMF) is the magnetic analog of electromotive force in circuits. It drives magnetic flux through a magnetic path and is directly proportional to the number of turns and the current through those turns. Calculating MMF is a foundational step in designing inductors, solenoids, and transformers.
Given Data / Assumptions:
- Number of turns N = 150 turns.
- Current I = 2 A.
- Use F = N * I with F in ampere-turns (At).
Concept / Approach:The greater the product of turns and current, the stronger the magnetizing force. While material properties and geometry affect resulting flux, MMF itself is purely a function of windings and current, independent of core type in the basic calculation.
Step-by-Step Solution:Write the formula: F = N * I.Substitute: F = 150 * 2 = 300 At.Therefore, MMF = 300 ampere-turns.
Verification / Alternative check:Units check: turns × amperes → ampere-turns; no conversions needed.
Why Other Options Are Wrong:13.33 mAt: off by orders of magnitude; milli-At inappropriate here.75 At: corresponds to 150 * 0.5 A, not given.152 At: not any simple combination of the provided values.
Common Pitfalls:Confusing MMF with magnetic field intensity H; H also depends on magnetic path length: H = F / l. Here only MMF is requested.
Final Answer:300 At