【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.
【单选题】无限长直圆柱 面 ,半径为 a ,沿轴向均匀流有电流 。 设圆柱 面 内 ( r a ) 的磁感强度为 B 2 ,则有: ( )
C.
B 1 与 r 成正比 , B 2 与 r 成反比
【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
【单选题】在乳腺癌和前列腺癌常见。患者对化疗或放疗有较好的治疗反应,治疗后6个月内临床上有改善,但骨显像似有恶化的表现(最明显在治疗后3个月),称之为
【判断题】将pH=3和pH=5的两种溶液等体积混合后,其pH变为4。( )
【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.
【简答题】These days computer s have become more and more popular in many cities and towns. A lot of small shops along busy 1 have changed into computer houses in order to get more ( 2) These places a...