A magnetic field has a flux density of 5000 µT across a uniform cross-sectional area of 300 mm². Calculate the total magnetic flux Φ present (state the result in webers or submultiples).
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A16.67 mWb
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B5.0 µWb
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C3.0 mWb
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D1.5 µWb
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E0.15 mWb
Answer
Correct Answer: 1.5 µWb
Explanation
Introduction / Context:Relating magnetic flux density (B) to total flux (Φ) through an area is a basic step in magnetic circuit calculations for transformers, inductors, and sensors. Flux determines induced voltages and is central to Faraday’s law and core saturation considerations.
Given Data / Assumptions:
- B = 5000 µT (microtesla).
- A = 300 mm^2 (square millimeters), area is uniform and perpendicular to flux lines.
- Flux Φ = B * A for uniform fields.
Concept / Approach:Use the relation Φ = B * A. Convert all quantities to SI units: tesla (T) for B and square meters (m^2) for area. Then multiply to get webers (Wb), the SI unit of flux.
Step-by-Step Solution:Convert B: 5000 µT = 5000 * 10^-6 T = 0.005 T.Convert A: 300 mm^2 = 300 * 10^-6 m^2 = 3.0 * 10^-4 m^2.Compute Φ: Φ = B * A = 0.005 * 3.0 * 10^-4 = 1.5 * 10^-6 Wb.Express in submultiples: 1.5 * 10^-6 Wb = 1.5 µWb.
Verification / Alternative check:Check units: T * m^2 = (Wb/m^2) * m^2 = Wb; magnitude is small and consistent with milli/µT fields and mm^2 areas.
Why Other Options Are Wrong:milliweber values (0.15–16.67 mWb) are three to four orders of magnitude larger than the correct microlevel result.
5.0 µWb assumes A = 1000 mm^2 (not given).
Common Pitfalls:Forgetting unit conversions (µT to T; mm^2 to m^2) leads to answers off by factors of 10^3 or 10^6. Always convert before multiplying.
Final Answer:1.5 µWb