【简答题】真空中有一根半径为r的无限长直圆柱形导线,其轴线OO'沿铅垂方向.沿轴线方向通有电流I,电流均匀分布于横截面内,在距轴线3r处有一个电荷量为-e的电子,沿平行于OO'轴方向以速度v向下运动,如图所示.求电子所受的磁场力.
【判断题】REVCLOUD该命令用于建立一个修正阴影,它可由一个由连续弧构成的多段线形成
【单选题】More and more shops use the paper bags to take the place of the ones.
【判断题】半径为R的无限长直圆柱面导体,沿圆柱面轴向通有恒定电流I ,电流均匀分布。以r 表示场点到圆柱面轴线的距离,则圆柱面外磁感应强度大小为
【判断题】半径为R的无限长直圆柱面导体,沿圆柱面轴向通有恒定电流I ,电流均匀分布。以r 表示场点到圆柱面轴线的距离,则圆柱面内磁感应强度大小为
【判断题】从赤道处出发,沿着一定的方位角出发的大地线,一定不会回到原来的点
【简答题】Online shopping is becoming more
and more popular for a number of reasons; prices are often lower online and
you don’t have to queue up in busy shops.
【简答题】Online shopping is becoming more and more popular for a number of reasons; prices are often lower online and you don’t have to queue up in busy shops.
【单选题】With Christmas ______, more and more people come to shops to buy gifts.