lǎo / shī / xiān / jiǎng / jiě / kù / lún / jì / de / gōng / zuò / yuán / lǐ / zài / ràng / dà / jiā / kāi / shǐ / shí / yàn

老师先讲解库仑计的工作原理，再让大家开始实验。

The teacher first explained how a voltameter works and then had everyone begin the experiment.