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My family
Hello ! everyone . I am Vera . I will graduate from Wuhan Textile University in a month . Today , I want to talk about my family . I am the smallest in my family . I have two brothers , and they wereare married . My second brother has a son named Tongtong , he is two years old , and he is living with my mother . We know , most of the babies look whilewhite , but he is very black . Maybe he just looks like his father . And he is fat , sometimes I can't hold him . His younger brother or sister waswill be born after three months . Maybe you will be surprised . But there is another thing is that my eldest sister-in-law had has two months' pregnancy . When she or he was born just is the Sprng Festival She or he will be born in the Spring Festival. So , there will be three babies in my family this year . I think that will be lively and noisy . And my mother will be very busy and hard . But I'm worried about my mother . Because her foot wounded several years ago , so she can't walk for a long time . I hope she would not so tired . My dad had a dog named Bladkie . He is was loyal and friendly .He lived with us for 11 years . He like liked to play with us and follow us . Everytime when we came back , he came out of room to meet us and He he remembered us . But he was died when I was in high school . I don't forget him forever . My brother had sereral several dogs these years , but I think Blackie is the best .
I correct it from my point of view:)
0 votedMay 4, 20131物理实验,实验原理
大家好!我有个愿望,就是写完我该写的物理报告。请你们帮助我改一下我的中文。其实,我不仅为了学习物理才会写这些,而也是为了练习中文。
1一般介绍
所谓霍尔效应,它是这样一个现象:
在将通有电流I的导体置于磁场B中的情况下,在导体的两端之间产生出现与电流和磁场方向垂直的电压。这个效应可以应用在比如在电子学中是可以,来测出测量磁感应强度应用的。
2理想条件下效应的解释
这个现象可以用洛仑兹力来解释.若在样品(你说的样品是指某一个导体试样吧?)的两端,按图示加一定的电压,则产生沿着样品并垂直于磁场的恒定的电流I. 载流子(电子)在磁场里运动时受到往向下的洛仑兹力F(B).于是载流子往向下运动。可是由于同性载流子之间有斥力。所以电子往向下的运动产生对与洛仑兹力反向的附加电场E。换句话说,载流子越往下,电场向着洛仑兹力的力F(G)也越大。终于最终载流子一定达到运态运动平衡状态。此时有如下关系: (方程)
到在这里引进一些名物参数: 设样品长度为l,宽为b,厚为d, 载流子浓度为n。在使用这样名物时利用这些参数,电流I可以表达为:(方程) 这里只要用(方程)来表达电势差就可以去得出UH的关系式为:(方程) 。 把方程中的因子-1/ned称为霍尔灵敏度,且用记号符号KH来表示它。从最后的公式不难看出,UH与IB乘积成正比,与d成反比。这就说明,比如样品越薄电压UH越大。还可以看出重要结果: 上端和下端电势的高低不但随电流I的换向而换向,而且也随磁场B的换向而换向。还有,如果公式所含有的量中只有一个量为末未知量,则当然可以把它按公式有剩下量确定这个量出来。
3.实际运用和要注意的几个负效应
事实上,样品上产生的电压U并非是上列所述的霍尔电压。这就是因为除了霍尔效应本身以外还存在几个产生附加电势差的负效应。比如因为载流子速度不同,所以它们所受的受大洛仑兹力也不同。结果使速度高的载流子趋向一侧,速度低的载流子趋向另一侧,从而产生附加电势差Ue。刚描述的称为爱廷豪森-效应。另一种负效应就是名称所谓的"能斯脱-效应"。能斯脱-效应出现原因如下:由于在M点与N点的电阻不同,所以则发热程度也不同。在这个种情况下,载流子有由高温区域向低温区域扩散,所以出现加附电压Un。并且为了由温度差而引起运动的载流子的速度不同,所以又会发生跟爱廷豪森类似的"里纪-勒杜克"-效应。这些负效应的影响上还加上另一个元素。由于材料本身的不均匀及工艺的限制,使P和S无法确切地接在同一等位面上(见图)。因此还要注意附加电势Uo.下列的窍门把刚描述的负效应引起的电势差从U中除去。只要把U在B与I的两样方向下测出来(这句话我没看懂,你是要表达:分别测量出U、B、I吗?),以后合当的和起来然后经过适当的计算,就可以得出一个仅仅地包括由Ue表示达U的一个公式。(窍门,方程) 并且Ue远小于Uh,使Ue是可以忽略的。结果实现很清晰的地计算出来霍尔电压Uh.你写的非常好!我也学过物理,但是我很讨厌物理实验,哈哈。这么改逻辑上更通顺了。
0 votedMay 4, 20132
