A.磁效應(yīng)B.磁場C.電場D.熱效應(yīng)
A.L1+L2B.L1+L2+MC.L1+L2–MD.L1+L2+2M
A.L1+L2B.L1-L2C.L1+L2+2MD.L1+L2-2M