Magnetic quantities — unit check: Is the SI unit of magnetic flux the weber (symbol Wb)?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Understanding magnetic units is essential for interpreting transformer ratings, generator equations, and sensor datasheets. Magnetic flux, flux density, and field strength each have distinct SI units: weber (flux), tesla (flux density), and ampere per meter (field strength).


Given Data / Assumptions:

  • The claim is about the unit of magnetic flux.
  • We work in SI (International System of Units).
  • No frequency- or geometry-specific caveats alter the unit itself.


Concept / Approach:
Magnetic flux Φ quantifies the total magnetic field passing through a surface. In SI, 1 weber is defined such that 1 weber per square meter equals 1 tesla (the unit of flux density). Faraday’s law links changing flux to induced voltage: e = –N * dΦ/dt, which supports unit consistency in electrical machines and inductive sensors.


Step-by-Step Solution:

Recall definitions: Φ in webers (Wb), B in teslas (T), H in A/m.Relate quantities: B = Φ / A for uniform fields, so 1 T = 1 Wb/m^2.Check machine law: e = –N * dΦ/dt → volt = turns * weber per second, dimensionally consistent.Conclude: the weber is the correct SI unit for magnetic flux.


Verification / Alternative check:
Unit relationships: 1 Wb = 1 V·s. Converting via Faraday’s law confirms the linkage between mechanical motion, changing flux, and induced voltage.


Why Other Options Are Wrong:
“Incorrect” contradicts SI. Frequency and cgs considerations do not redefine SI units. Coil turns affect induced voltage magnitude via N, not the unit of flux.


Common Pitfalls:
Confusing flux (Wb) with flux density (T) and with field strength (A/m); mixing SI and cgs terms like gauss and maxwell without conversion.


Final Answer:
Correct

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