如图所示,D是一只理想二极管,AB是平行板电容器,在电容器两极间有一带电微粒P处于静止状态,当两极板A和B间的距离增大一些的瞬间(两极板仍平行),带电微粒P的运动及电容器的电压?电量情况是( )
A．带电量减少
B．因与电源相连,所以电压不变
C．电场强度增大
D．P仍静止不动
答案：D
电容器与电源保持相连，电容器的电压不变，板间距离增大，电容减小，电容量的电量要减小，放电，但由于二极管的作用只允许电流从a流向b，电容器的电量无法减小，根据推论板间电场强度E=
，Q、S、?不变，则改变d，E不变，电荷P受的电场力不变，仍静止．U=Ed，因为A和B间的距离增大所以电压增大，故D正确．
故选D
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| Today the problem of environment has become more and more serious. Every day, every hour, the air, forests, soil, oceans and fresh 1 are becoming dirtier and dirtier. There are two 2 for the problem: the excessive (过度) use of natural resources and pouring a lot of 3 waste in the course of production. Yet, man 4 great progress in environmental protection. Scientists and inventors are trying to develop 5 engines for automobiles. Governments of many countries have made 6 to protect the natural resources. More and more people have realized the importance of environmental protection and are doing what they can to protect our surroundings. Still more ways 7 to solve the problem. People should be educated in 8 modern methods to protect the environment and learn to make clever use of recycling our natural resources. The government of all 9 should take ways to fight against pollution _ 10 _ protecting the environment is not only protecting our home but also the civilization (文明) of the humankind. | |||
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