题目内容
如图所示,宽L=1m、倾角
的光滑平行导轨与电动势E=3.0V、内阻r=0.5
的电池相连接,处在磁感应强度
、方向竖直向上的匀强磁场中。质量m=200g、电阻R=1
的导体ab从静止开始运动。不计期于电阻,且导轨足够长。试计算:
(1)若在导体ab运动t=3s后将开关S合上,这时导体受到的安培力是多大?加速度是多少?
(2)导体ab的收尾速度是多大?
(3)当达到收尾速度时,导体ab的重力功率、安培力功率、电功率以及回路中焦耳热功率和化学功率各是多少?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241146463133693.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646267278.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646267223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646282347.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646267223.gif)
(1)若在导体ab运动t=3s后将开关S合上,这时导体受到的安培力是多大?加速度是多少?
(2)导体ab的收尾速度是多大?
(3)当达到收尾速度时,导体ab的重力功率、安培力功率、电功率以及回路中焦耳热功率和化学功率各是多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241146463133693.jpg)
(1)受安培力为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646345304.gif)
加速度为:
,即导体做匀减速运动.
(2)收尾速度![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646376349.gif)
(3)导体ab的重力功率、安培力功率和电功率大小相等,即:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646391290.gif)
回路中焦耳热功率和化学功率分别为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646407400.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646345304.gif)
加速度为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646360324.gif)
(2)收尾速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646376349.gif)
(3)导体ab的重力功率、安培力功率和电功率大小相等,即:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646391290.gif)
回路中焦耳热功率和化学功率分别为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646407400.gif)
(1)闭合开关前,导体ab在3s末的速度为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646423443.gif)
导体ab的感应电动势为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646438509.gif)
闭合开关时,导体所受安培力为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646454564.gif)
加速度为:
,即导体做匀减速运动.
(2)当a=0时,导体的速度最小,即为收尾速度,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646485806.gif)
(3)当导体以收尾速度匀速运动时,导体ab的重力功率、安培力功率和电功率大小相等,即:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646501434.gif)
同理,还有:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646516498.gif)
则电路中的电流为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646532497.gif)
所以,回路中焦耳热功率和化学功率分别为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646532612.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646423443.gif)
导体ab的感应电动势为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646438509.gif)
闭合开关时,导体所受安培力为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646454564.gif)
加速度为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646469582.gif)
(2)当a=0时,导体的速度最小,即为收尾速度,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646485806.gif)
(3)当导体以收尾速度匀速运动时,导体ab的重力功率、安培力功率和电功率大小相等,即:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646501434.gif)
同理,还有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646516498.gif)
则电路中的电流为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646532497.gif)
所以,回路中焦耳热功率和化学功率分别为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114646532612.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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