EMEC

$r_{m}=({\frac {1}{2}}){\frac {OD+ID}{2}}$

$H_{m}=({\frac {Ni}{l_{m}}})$

Failed to parse (SVG with PNG fallback (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle H_m=(\frac{20 x 2.5}{.141}= 354.6 A\/m)}