题干

如图所示,两个等量异号点电荷M、N分别固定在A、B两点,F为AB连线中垂线上某一点,O为AB连线的中点.且AO=OF,E和φ分别表示F处的场强大小和电势.将某试探负点电荷由F处静止释放时,其电势能和加速度大小分别用ε和a表示,取无穷远处为电势零点.若将负点电荷N移走,则(   )

A:E不变

B:φ升高

C:ε变小

D:a变大

上一题 下一题 0.0难度 选择题 更新时间:2019-08-28 06:08:35

答案(点此获取答案解析)

B,C

同类题3

通读下面短文,掌握其大意,然后在每小题所给的四个选项中,选出一个最佳答案。

    My six-year-old granddaughter, Cindy, and I stopped at a food shop for some bread. Cindy had1 it for several days. As we were going out of the door, a young teenage boy was coming in.

    The boy had no hair on the side of his head but a set of blue spiked(成锥形的) hair on top of it. His nose was 2 , and a ring ran through the hole. A chain went across his face and it was connected to his earring. He held a skateboard under one arm and a basketball under the other.

    Cindy, who was walking ahead of me, 3stopped when he saw the boy. I thought he had  4 my granddaughter. I was wrong. My granddaughter backed up against the door and opened it as wide as it would go. Now I came face to face with the young man. I stepped aside and let him5. He replied very6, "Thank you very much."

    On our way to the car, I 7 Cindy for holding open the door for the boy. To my surprise, she didn't seem to be troubled by the young boy's 8 . But I wanted to make sure. I wanted to be ready to talk about freedom of expressing themselves and allowing people's  9   .

    As it turned out, the person  10needed the talk was me. The only thing Cindy noticed about the boy was the fact that his arms were   11 . "He held a skateboard under one arm and a basketball under the other. He would have a 12  time to open the door, " said Cindy.

    I just paid attention to the partially shaved (部分剃光的)head, the set of spiked hair, the piercing and the chain. She saw a person carrying   13 under each arm and heading toward a(n) 14 door.

    What my granddaughter said reminded me that I should change my ways of judging people and 15 my granddaughter to be open-minded and warm-hearted.