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I have twelve bananas.
The box was heavy but he to carry it.
如图所示,A、B两个闭合线圈用同样的导线制成,匝数均为10匝,半径rA=2rB,
图示区域内有匀强磁场,且磁感应强度随时间均匀减小.
实际划分东西半球的界线是( )