题目内容
(2011·福建理综·T17)如图,足够长的U型光滑金属导轨平面与水平面成
角(0<
<90°),其中MN与
平行且间距为L,导轨平面与磁感应强度为B的匀强磁场垂直,导轨电阻不计。金属棒
由静止开始沿导轨下滑,并与两导轨始终保持垂直且良好接触,
棒接入电路的电阻为R,当流过
棒某一横截面的电量为q时,棒的速度大小为
,则金属棒
在这一过程中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411084325925.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107527297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107527297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107808399.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107870370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107870370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107870370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141108151265.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141107870370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411084325925.jpg)
A.运动的平均速度大小为![]() |
B.下滑的位移大小为![]() |
C.产生的焦耳热为![]() |
D.受到的最大安培力大小为![]() |
选B.
由E=BLV、
、F安=BIL可得棒的速度为V时的安培力为
,D错;对导体棒受力分析如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411088681368.jpg)
据牛顿运动定律判断可得导体棒的运动情况如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411089151281.jpg)
由图可知导体棒这一过程的平均速度大于
,A错;由法拉第电磁感应定律得到导体棒这一过程的电量
,因此导体棒下滑的位移
,B对;由能量关系可得这一过程产生的焦耳热
,C错,故选B.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141108759516.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141108806645.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411088681368.jpg)
据牛顿运动定律判断可得导体棒的运动情况如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411089151281.jpg)
由图可知导体棒这一过程的平均速度大于
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141108931419.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141108978680.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141109056662.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411091021253.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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