挑战习题
1/5单选题
难度:

1.关于电磁铁,下面说法中正确的是(  )
A 电磁铁是根据电磁感应原理制作的
B 电磁继电器中的磁体,必须用电磁铁
C 电磁继电器中的磁体,可以用永磁体,也可以用电磁铁
D 电磁铁中的铁芯,可以用钢棒代替
提示1:
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正确答案:Qg==
QeOAgeeUteejgemTgeaYr+WIqeeUqOeUtea1geeahOejgeaViOW6lOWItuaIkOeahO+8jOaVhemAiemhuUHplJnor6/vvJs8YnI+QuOAgeeUteejgee7p+eUteWZqOS4reeahOejgeS9k++8jOW/hemhu+eUqOeUteejgemTge+8jOmAmui/h+eUtea1geeahOmAmuaWreaOp+WItuejgeaAp+eahOacieaXoO+8jOS4jeiDveeUqOawuOejgeS9k++8jOaVhemAiemhuULmraPnoa7vvJs8YnI+Q+OAgeeUteejgee7p+eUteWZqOS4reeahOejgeS9k++8jOW/hemhu+eUqOeUteejgemTge+8jOmAmui/h+eUtea1geeahOmAmuaWreaOp+WItuejgeaAp+eahOacieaXoO+8jOS4jeiDveeUqOawuOejgeS9k++8jOaVhemAiemhuUPplJnor6/vvJs8YnI+ROOAgemSouajkuaYr+awuOejgeS9k++8jOejgeWMluWQjuS4jeWuueaYk+mAgOejge+8jOaVheS4jeiDveeUqOmSouajkuS7o+abv+mTgeiKr++8jOaVhemAiemhuUTplJnor6/vvJs8YnI+5pWF6YCJQu+8jg==