A:青蛙
B:兔
C:鹿
D:棕熊
—Excuse me. Could you tell me_____ get to the nearest post office?
—Sorry ,I am new here
如图所示,平行板电容器的电容为C,带电荷量为Q,板间距离为d,今在两板的中点处放一电荷q,则它所受电场力的大小为()
夏天,从冰箱中取出瓶装矿泉水时,会发现瓶外壁“出汗”,这是( )