Magnetism fundamentals: Magnetic flux is defined as the total amount of magnetic field passing through a surface. In SI units, magnetic flux is measured in what unit?

Introduction / Context:
Magnetic quantities often confuse beginners because multiple units and legacy terms exist. Distinguishing magnetic flux (Φ), flux density (B), and field strength (H) is vital for analyzing transformers, inductors, and machines, and for converting between device specifications and formulas.

Given Data / Assumptions:

• Magnetic flux Φ is a scalar quantity representing the total field passing through an area.
• SI unit for flux is the weber (Wb).
• Flux density B is measured in tesla (T), where 1 T = 1 Wb/m^2.

Concept / Approach:
Flux quantifies the ”amount” of magnetic field, analogous to electric flux in electromagnetism. In the SI system, Φ is measured in webers. Older CGS literature uses the maxwell, where 1 Wb = 10^8 maxwells. Tesla measures flux density, not flux. Therefore, when a question asks “what is magnetic flux,” the correct unit is the weber and descriptions referring to “lines of force” are colloquial placeholders mapping to webers.

Step-by-Step Solution:

Verification / Alternative check:
Textbook relationships for inductors (Φ = L * I / N in simplified cases) and transformer EMF (E = N * dΦ/dt) consistently use webers for flux to yield volts for induced EMF.

Why Other Options Are Wrong:

• Maxwell: A CGS unit, not SI; included here as a distractor.
• Tesla: Unit of flux density, not total flux.
• “Flux density”: A different physical quantity; the option is self-contradictory.

Common Pitfalls:
Mixing up flux and flux density when reading datasheets; overlooking unit conversions between CGS and SI.

Final Answer:
the number of lines of force in webers