<참고자료>
[1] https://blogs.scientificamerican.com/observations/why-carbon/
[2] https://terms.naver.com/entry.nhn?docId=1106468&cid=40942&categoryId=32251
[3] https://terms.naver.com/entry.nhn?docId=945238&cid=47337&categoryId=47337
<이미지>
[1] http://blog.naver.com/PostView.nhn?blogId=rhselan153&logNo=220208255074
[2] https://librewiki.net/wiki/%EC%82%B0%EC%86%8C
[3] https://www.alamy.com/stock-photo/ferrite.html