在奥斯特实验中我们发现:在直导线周围放上小磁针,当导线中通电时,小磁针转动.这说明 ____,电流通过它产生的 ____对磁体施加力的作用,当电流方向改变时, ____方向改变.
我国水旱灾害频繁的根本原因是( )
你能够利用一张白纸和一把刻度尺测出一个凸透镜的焦距吗?请简述测量步骤.
根据句意及首字母提示完成单词
①He asked p____ to leave the room.
② The government still face very s____ difficulties.
③We p____ £35 for each ticket.
④The country is facing great economic d____.
⑤Peter o____ to teach them water-skiing.