<https://www.coursera.org/lecture/dianci-2/6-14jiang-zuo-zhi-si-cong-wu-li-li-xian-dao-dian-ci-chang-li-lun-HVcJS#lecture>
<http://schema.org/name>
"6.14讲座之四：从物理力线到电磁场理论"
<https://www.coursera.org/lecture/dianci-2/6-14jiang-zuo-zhi-si-cong-wu-li-li-xian-dao-dian-ci-chang-li-lun-HVcJS>