In magnetic field terminology, what is the correct SI unit for magnetic flux density B (i.e., webers per square meter)?
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Amagnetomotive force
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Ba weber
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Ca maxwell
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Da tesla
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Ean ampere per meter
Answer
Correct Answer: a tesla
Explanation
Introduction / Context:Magnetic quantities have distinct symbols and SI units. Confusing magnetic flux, flux density, and field intensity leads to errors in analysis and design. Flux density B measures how much magnetic flux passes per unit area, a key parameter for core sizing and saturation considerations.
Given Data / Assumptions:
- B denotes magnetic flux density.
- SI base relation: B = Φ / A, with Φ in webers (Wb) and A in square meters (m^2).
- Standard SI unit naming conventions apply.
Concept / Approach:Because B = Φ/A, its unit is weber per square meter. The SI derived unit name for Wb/m^2 is the tesla (T). Other related quantities include H (magnetic field strength) in A/m and Φ (flux) in webers. Non-SI cgs units like gauss are sometimes used (1 T = 10,000 gauss).
Step-by-Step Explanation:Start with definition: B = Φ / A.Units: Φ in Wb, A in m^2, so B in Wb/m^2.By SI naming, Wb/m^2 is called tesla (T).Therefore, the correct unit is tesla.
Verification / Alternative check:Dimensional analysis and standard references list B's SI unit as tesla. Also, the relationship B = μ * H yields units T = (H/m) * (A/m) = N/(A·m), consistent with tesla's alternative forms.
Why Other Options Are Wrong:
- Magnetomotive force (MMF) is measured in ampere-turns, not B.
- Weber is the unit of flux Φ, not flux density.
- Maxwell is a cgs unit of flux, not SI and not B.
- Ampere per meter is the unit of H (field intensity), not B.
Common Pitfalls:
- Mixing B and H or their units (tesla vs ampere per meter).
- Confusing flux (Wb) with flux density (T).
Final Answer:a tesla