如图所示，电源电动势为E，内阻r=R，定值电阻R₁和R₂的阻值均为R．平行板电容器接在R₂两端，两极板长度和距离均为d，足够大屏幕与电容器右端距离为d，OO₁为电容器中心轴线．一个不计重力、质量为m、电荷量为q的带正电粒子从O点以一定的初速度沿OO₁方向射入电场，离开电场时的位置与电容器下极板的距离为 $\frac{d}{4}$ ．

      On weekdays, David gets up at 6:30.He has breakfast at seven and then he goes to school by bus. He gets there at 7:15. He doesn't like to be late. Classes begin at 8:00. He has lunch at twelve at school. He goes home at 5:30 in the afternoon. On weekends, he gets up at about 8:00 and makes breakfast for his family. His parents like him very much.

看图填一填。