The S.l unit of magnetic flux density is

Analyze the question: It asks for the SI unit of magnetic flux density (also called magnetic field strength, symbol B).

Explain the concept: Magnetic flux density is the magnetic flux passing through a unit area perpendicular to the field:

B = Φ / A

where

• Φ = magnetic flux (measured in webers, Wb)
• A = area (measured in m²)

Show the solution: Unit of B = weber / metre² = Wb/m²

This unit is given the special name tesla (T), so 1 T = 1 Wb m⁻².

In base SI units, 1 T = 1 kg s⁻² A⁻¹.

Check the other options:

• A. Farad is the unit of capacitance.
• B. Henry is the unit of inductance.
• C. kg m⁻³ is the unit of density, which is mass per volume and has nothing to do with magnetism.
• E. Weber is the unit of magnetic flux, not flux density. This is the most common trap.

Answer: The correct option is D. tesla.

Tip: Remember the word "density" means "per unit area" here. Flux density is flux per area, so Weber → Weber per m² → Tesla. A quick way to remember it: Tesla = Thickness of field lines per area, while Weber = Whole flux.