题目内容
如图所示,MN和PQ是竖直放置相距1m为的滑平行金属导轨(导轨足够长,电阻不计),其上方连有
=9Ω的电阻和两块水平放置相距d=20cm的平行金属板A.C,金属板长1m,将整个装置放置在图示的匀强磁场区域,磁感强度B=1T,现使电阻
=1Ω的金属棒ab与导轨MN、PQ接触,并由静止释放,当其下落h=10m时恰能匀速运动(运动中ab棒始终保持水平状态,且与导轨接触良好).此时,将一质量
=0.45g,带电量q=1.0×
的微粒放置在A.C金属板的正中央,恰好静止.g=10m/
).求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958452949.gif)
(1)微粒带何种电荷?ab棒的质量
是多少?
(2)金属棒自静止释放到刚好匀速运动的过程中,电路中释放多少热量?
(3)若使微粒突然获得竖直向下的初速度
,但运动过程中不能碰到金属板,对初速度
有何要求?该微粒发生大小为
的位移时,需多长时间?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958046956.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958046960.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958062956.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958249998.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958264938.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958452949.gif)
(1)微粒带何种电荷?ab棒的质量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958654958.gif)
(2)金属棒自静止释放到刚好匀速运动的过程中,电路中释放多少热量?
(3)若使微粒突然获得竖直向下的初速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958670945.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958670945.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159586861133.gif)
(1)0.1kg (2)5J (3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159588571123.gif)
(1)对微粒:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159588731375.gif)
则I=
=1A ε=
=10(V) 对![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159589511265.gif)
(2)ε=BLV
V=
/BL=10m/s ∴ΔQ=mgH-
=5(J)
(3)R=
<0.1 得:
<
=0.02(m/s)
又:
即粒子经过
的时间
·9π (n=0,1,2……)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159588731375.gif)
则I=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159589201006.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159589351028.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159589511265.gif)
(2)ε=BLV
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958966931.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115958982921.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159590441037.gif)
(3)R=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159590601043.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115959060958.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115959076989.gif)
又:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159592471219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115959263972.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241159588571123.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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