In the demonstrate video, the experimental equipment is presented and experimental principles are
explained first, and then experiment processes are operated by the teacher. The demonstration video keeps
pace with the experiment PPT, which allows students to follow the experiment procedure more closely and
encourage their interest in learning. Besides, special local magnifier function is designed in the video, as
shown in Fig.2 (a). This allows students to observe the operating action of relays and record the data
clearly.