Electromagnetic Field
noun
A 磁場 is a "magnetic field." An electricity version of this is an electromagnetic field.
This is a jukugo word that uses the on'yomi readings for the first two kanji and the kun'yomi reading of the third. You should be able to read this on your own. Will of course help to know 磁場 as well.
私の父は、電磁場発生装置の特許を持っているんですが、私はそれが何のためのものなのかよく分かりません。
My father has a patent for an electromagnetic field generator, but I’m not sure what it’s for.