A.20﹪ B.30﹪ C.25﹪ D.35﹪
A.0.10~0.20mm B.0.175~0.25mm C.0.20~0.30mm D.0.15~0.25mm
A.電感原理 B.電熱效應(yīng) C.光電感應(yīng)原理 D.電磁效應(yīng)