题目内容
真空中有两根长直金属导线平行放置,其中一根导线中通有恒定电流.在两导线所确定的平面内,一电子由P点开始运动到Q的轨迹如图中曲线PQ所示,则一定是:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250024044042547.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250024044042547.jpg)
A.ab导线中通有从a到b方向的电流 |
B.ab导线中通有从b到a方向的电流 |
C.cd导线中通有从c到d方向的电流 |
D.cd导线中通有从d到c方向的电流 |
C
试题分析:注意观察图象的细节,靠近导线cd处,电子的偏转程度大,说明靠近cd处偏转的半径小,洛伦兹力提供电子偏转的向心力,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002404435761.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002404451693.png)
故选:C
![](http://thumb2018.1010pic.com/images/loading.gif)
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