如图所示,在光滑绝缘的水平面上方,有两个方向相反的水平方向的匀强磁场,磁场范围足够大,磁感应强度的大小左边为2B,右边为3B,一个竖直放置的宽为L。长为3L、单位长度的质量为m、单位长度的电阻为r的矩形金属线框,以初速度v垂直磁场方向从图中实线位置开始向右运动,当线框运动到虚线位置(在左边磁场中的长度为L。在右边磁场中的长度为2L)时,线框的速度为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmfrac%3E%3Cmn%3E1%3C%2Fmn%3E%3Cmn%3E3%3C%2Fmn%3E%3C%2Fmfrac%3E%3Cmi%3Ev%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
, 则下列判断正确( )
的是( )
![](http://tikupic.21cnjy.com/2023/04/14/c9/fc/c9fc8925aca44125077d2a0609ff0588_454x125.png)
- A、此时线框中电流方向为逆时针,线框中感应电流所受安培力为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmfrac%3E%3Cmrow%3E%3Cmn%3E13%3C%2Fmn%3E%3Cmsup%3E%3Cmi%3EB%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3Cmi%3EL%3C%2Fmi%3E%3Cmi%3Ev%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E24%3C%2Fmn%3E%3Cmi%3Er%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
- B、线框刚好可以完全进入右侧磁场
- C、此过程中通过线框截面的电量为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmfrac%3E%3Cmrow%3E%3Cmn%3E16%3C%2Fmn%3E%3Cmi%3Em%3C%2Fmi%3E%3Cmi%3Ev%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E5%3C%2Fmn%3E%3Cmi%3EB%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmfrac%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
- D、此过程中线框产生的焦耳热为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmfrac%3E%3Cmn%3E4%3C%2Fmn%3E%3Cmn%3E9%3C%2Fmn%3E%3C%2Fmfrac%3E%3Cmi%3Em%3C%2Fmi%3E%3Cmsup%3E%3Cmi%3Ev%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)