题目内容
(10分)载流长直导线周围磁场的磁感应强度大小为B=kI/r,式中常量k>0,I为电流强度,r为距导线的距离。在水平长直导线MN正下方,矩形线圈abcd通以逆时针方向的恒定电流,被两根等长的轻质绝缘细线静止地悬挂,如图所示。开始时MN内不通电流,此时两细线内的张力均为T0。当MN通以强度为I1的电流时,两细线内的张力均减小为T1;当MN内的电流强度变为I2时,两细线的张力均大于T0。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031021448.png)
(1)分别指出强度为I1、I2的电流的方向;
(2)求MN分别通以强度为I1和I2电流时,线框受到的安培力F1与F2大小之比;
(3)当MN内的电流强度为I3时两细线恰好断裂,在此瞬间线圈的加速度大小为a,求I3。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031021448.png)
(1)分别指出强度为I1、I2的电流的方向;
(2)求MN分别通以强度为I1和I2电流时,线框受到的安培力F1与F2大小之比;
(3)当MN内的电流强度为I3时两细线恰好断裂,在此瞬间线圈的加速度大小为a,求I3。
(1)
方向向左,
方向向右(2)
(3)
(方向向右)或者
(方向向左)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703118293.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703134324.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703149577.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031651075.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031801088.png)
试题分析:(1)当MN通以强度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703118293.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703212319.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703118293.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703134324.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703258358.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703134324.png)
(2)当MN中通以电流I时,线圈所受安培力大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703290908.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703305914.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703149577.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703336521.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703352620.png)
若加速度向下:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703368753.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027033831782.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031651075.png)
若加速度向上:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002703430726.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027034461817.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250027031801088.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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