题目内容
如图(a)所示的螺线管,匝数n=1500匝,横截面积S=20cm2,电阻
,与螺线管串联的外电阻
,
。方向向左,穿过螺线管的匀强磁场的磁感应强度按图(b)所示规律变化,求:
(1)电阻R2的电功率;
(2)a、b两点的电势(设c点电势为零)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241345525618028.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552436524.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552483584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552514597.png)
(1)电阻R2的电功率;
(2)a、b两点的电势(设c点电势为零)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241345525618028.jpg)
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552624629.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552655577.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552577719.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552624629.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552655577.png)
(1)由图(b)可知,螺线管中磁感应强度B均匀增加,其变化率为:
…………………………………1分
由法拉第电磁感应定律得:
………… ………………2分
通过回路的电流:
…………………………………2分
电阻
消耗的功率:
…………………………………2分
(2)依题意可知,
中感应电流方向从
流向![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553045283.png)
端电势高,
端电势低,
…………………2分
…………………………………1分
又
…………………………………2分
…………………………………1分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552702995.png)
由法拉第电磁感应定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241345527481190.png)
通过回路的电流:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552780921.png)
电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552826359.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552577719.png)
(2)依题意可知,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552936456.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553014299.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553045283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553092320.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553045283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553170795.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553201443.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552624629.png)
又
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134553294771.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134552655577.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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