A.電壓 B.電流 C.電阻 D.電功
A.N極應(yīng)與磁鐵的N極 B.S極應(yīng)與磁鐵的S極 C.N極應(yīng)與磁鐵的S極 D.N極應(yīng)與蓄電池的S極
A.0-5mm B.5-10mm C.6-10mm D.10-15mm