Electromagnetism is the link between electricity and magnetism, and the effects they have on each other. A changing electric current can make a magnetic field; a changing magnetic field can make an electric current. That two-way relationship is why we have motors, generators, and radio.

Electromagnetism「Electromagnetism」 是 the link between電和磁之間的關聯 electricity and magnetism，and還有 the effects它們對彼此 they have on each other產生的影響。A changing electric current一個變動的電流 can make可以產生 a magnetic field一個磁場；a changing magnetic field一個變動的磁場 can make也可以產生 an electric current一個電流。That這種 two-way relationship雙向的關係 is就是 why我們之所以會有 we have motors, generators, and radio馬達、發電機和收音機的原因。

As a school subject, electromagnetism is the chapter that puts those ideas together. Though actually, in casual talk people sometimes use it as a big vague word for “anything with electricity and magnets,” which is close but fuzzier than the physics meaning.

As a school subject當作學校科目來看，electromagnetism「electromagnetism」 是就是 the chapter把這些概念放在一起的那一章 that puts those ideas together。Though actually不過其實，in casual talk在日常口語裡 people大家 sometimes有時候 use it把它用 as a big vague word當成一個籠統的大字 for "anything with electricity and magnets,"泛指「任何跟電和磁有關的東西」，which而這 是接近 close but但比 fuzzier比物理學上的意思模糊 than the physics meaning。

It is a science-class noun, more formal than electromagnet, which names a single object.

It它 是 a science-class noun一個理科課堂用的名詞，more formal比……更正式 than electromagnet比「electromagnet」，which它 names指的是 a single object單一一個物體。