从北半球的春分日到夏至日,太阳直射点在地球上的运动过程是
A:赤道→南回归线
B:赤道→北回归线
C:北回归线→赤道
D:南回归线→赤道
In summer we like staying in the room w____ window faces north.
_____the scientists have done lots of research on Mars, there is still much waiting to be discovered.
如图所示,线圈为100匝,在2s内穿过线圈的磁通量由2Wb均匀增大到4Wb,求:
⑴这2s时间内线圈产生的感应电动势;
⑵如果线圈回路的总电阻为100Ω,则感应电流是多大?