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【单选题】
变压器的初、次级电动势E1、E2和初、次级线圈匝数N1、N2之间的关系为()。A.
E 1 /E 2 =N 1 /N 2
B.
E 1 /E 2 =N 2 /N 1
C.
E 1 /E 2 =N 1 2 /N
D.
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