A toroid wound with 100 turns/m of wire carries a current of 3 A. The core of toroid is made of iron having relative magnetic permeability of μᵣ=5000 under given conditions. The magnetic field inside the iron is .

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(4) 1.88 T. Given: n=100 turns per metre, I=3 A, iron core with μᵣ=5000. Idea: inside a toroid the winding fixes the magnetic intensity H=nI, and the core responds with B=μ₀μᵣH. H=100×3=300 A m⁻¹. μ₀μᵣ=(4π×10⁻⁷)(5000)=6.28×10⁻³ T m A⁻¹. B=(6.28×10⁻³)(300)=1.885 T, that is about 1.88 T. Without the iron the same winding would give only μ₀H=3.8×10⁻⁴ T; the core multiplies it five thousand times, which is why electromagnets are wound on iron. So the field inside the iron is about 1.88 T.

A toroid wound with 100 turns/m of wire carries a current of 3 A. The core of toroid is made of iron having relative magnetic permeability of μᵣ=5000 under given conditions. The magnetic field inside the iron is ______.

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