Magnetic Field Strength (H)

H = N · I / l

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Result
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Formula

H = N × I / l

Description

Magnetic field strength (or magnetizing force) H is the MMF per unit length of the magnetic path. It describes how hard the coil drives the magnetic field, independent of the core material. The resulting flux density follows from B = µ₀µr·H, so H is the cause and B is the effect. It is central to reading B–H magnetization curves.

Variables

  • H — Magnetic field strength (A/m)
  • N — Number of turns
  • I — Current (A)
  • l — Magnetic path length (m)

Practical Notes

On a B–H curve the material saturates when increasing H no longer increases B. For a solenoid H = nI where n is turns per metre; for a toroid l is the mean magnetic path length.

Related Concepts

All Magnetics & Transformers formulas →
Transformer EMF Equation Transformer VA Rating Transformer Voltage Regulation Transformer Current Ratio Transformer Copper Loss Transformer Iron (Core) Loss Transformer Turns-per-Volt Transformer Impedance Matching

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