Encyclopedia Magnetica™

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Magnetic field strength H of rectangular current loop along its axis
$$ H(t,x) = I(t)· \frac{2}{π}·\frac{a·b}{\sqrt{4·x^2 + a^2 + b^2} }·\left(\frac{1}{4·x^2 + a^2} + \frac{1}{4·x^2 + b^2} \right) $$	(A/m)
where: $I(t)$ - current (A) at time $t$ (s), $a$ and $b$ - length of sides of the rectangular loop (m), $x$ - location (m) from the centre of the loop (the centre is located at point x = 0); assuming infinitely thin wire and a rectangular loop placed in a uniform medium; (use $a=b$ for a square loop)