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## Homework Statement

Hi all.

I'm trying to understand the H-field. From Ampére's law we have:

[tex]\oint {{\bf{H}} \cdot {\rm{d}}{\bf{l}}} = I_{free,enclosed}[/tex]

If I look at an object with zero free, enclosed current, the integral equals zero. The integral can be equal to zero even if

**H**is not zero. But if the integral equals zero and if

**H**is constant and parallel to d

**l**, I can take it outside the integral, and hence

**H**=0.

My question is: How do I know if

**H**is in the same direction as d

**l**and constant in magnitude?

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