题目内容
如图甲所示,不计电阻的平行金属导轨与水平夹角37°放置,导轨间距为L=1 m,上端接有电阻R=3 Ω,虚线OO′ 下方是垂直于导轨平面的匀强磁场.现将质量m=0.1 kg、电阻r=1 Ω的金属杆ab从OO′上方某处垂直导轨由静止释放,杆下滑过程中始终与导轨垂直并保持良好接触,杆下滑过程中的v-t图象如图乙所示.(取g=10 m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241334154126484.png)
求:(1)磁感应强度B;
(2)杆在磁场中下滑0.1s过程中电阻R产生的热量.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241334154126484.png)
求:(1)磁感应强度B;
(2)杆在磁场中下滑0.1s过程中电阻R产生的热量.
(1) B=2T (2)QR=3/160J
(1)有图乙得![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241334154581144.png)
0.1s前,mgsinθ-f=ma
0.1s后匀速运动,mgsinθ-f-FA="0" ,FA=BIL=
得B=2T
(2)方法一:磁场中下滑0.1 s过程中,电流恒定I=
=0.25A, QR=I2Rt=3/160J
方法二:x=vt=0.05m,下落高度h=xsinθ=0.03m,QR=3/4(mgh-fx)=3/160J
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241334154581144.png)
0.1s前,mgsinθ-f=ma
0.1s后匀速运动,mgsinθ-f-FA="0" ,FA=BIL=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133415521694.png)
(2)方法一:磁场中下滑0.1 s过程中,电流恒定I=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133415755598.png)
方法二:x=vt=0.05m,下落高度h=xsinθ=0.03m,QR=3/4(mgh-fx)=3/160J
![](http://thumb2018.1010pic.com/images/loading.gif)
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