【简答题】句型转换 1. Work hard,and you'll succeed. ______ _______,you will succeed. 2. After he finished his work,Henny went home. ________ _______ his work,Henny went home. 3. If heated,ice can turn into liquid. ...
【简答题】Reading the passage, and answer the question(阅读歌词,根据歌词,完成连线): When I was young I'd listen to the 1. radio Waiting for my 2. f avorite songs When they played I'd sing along It made me smile Those were ...
【单选题】如图所示为一种获得高能粒子的装置,环形区域内存在垂直纸面向外、大小可调节的均匀磁场,质量为 m ,电荷量为+ q 的粒子在环中做半径为 R 的圆周运动。 A 、 B 为两块中心开有小孔的极板,原来电势都为零。每当粒子顺时针飞经 A 板时, A 板电势升高为 U , B 板电势仍保持为零,粒子在两板间电场中得到加速,每当粒子离开 B 板时, A 板电势又降为零,粒子在电场一次次加速下动能不断增大,而...
A.
粒子从 A 板小孔处由静止开始在电场作用下加速,绕行 n 圈后回到 A 板时获得的总动能为 2 nqU
B.
在粒子绕行的整个过程中, A 板电势可以始终保持为+ U
C.
在粒子绕行的整个过程中,每一圈的周期不变
D.
为使粒子始终保持在半径为 R 的圆轨道上运动,磁场必须周期性递增,则粒子绕行第 n 圈时的磁感应强度为