题目内容
如图所示,光滑的导轨竖直放置,匀强磁场的磁感应强度为
T,磁场方向垂直导轨平面向外,导体棒
长
m,电阻
Ω,导轨的电阻不计,当导体棒紧贴导轨匀速下滑时,均标有“6V 3W”字样的两小灯泡恰好正常发光,求
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241144450391812.gif)
1、
的运动速度;
2、电路的电功率。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444976240.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444992223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445008278.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445023276.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241144450391812.gif)
1、
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444992223.gif)
2、电路的电功率。
⑴
7m/s
W
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445070199.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445086586.gif)
⑴设金属棒速度大小为
,因两灯泡能正常发光,两灯泡正常发光所需的电压为6V,知回路中路端电压
V,设灯泡的电阻为
,
,由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445210468.gif)
得
7m/s
解法一 两灯泡并联,流过金属棒
的电流等于流过两灯泡电流的和,
A,由
得金属棒的电功率
W,所以整个电路的电功率
W
解法二 金属棒匀速运动,金属棒
的重力与金属棒所受的安培力是平衡力,由能量守恒定律知,电路的电功率等于安培力
的功率,流过金属棒
的电流
A,
N,由第⑴问知,金属棒匀速运动的速度
7m/s,
安培力的功率
W
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445101185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445117392.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445132226.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445148681.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445164286.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445179625.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445210468.gif)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445070199.gif)
解法一 两灯泡并联,流过金属棒
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444992223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445257725.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445273301.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445288239.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445086586.gif)
解法二 金属棒匀速运动,金属棒
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444992223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445351200.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114444992223.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445257725.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445429597.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445070199.gif)
安培力的功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114445460481.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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