题干

如图是某型号电动轮椅工作原理示意图.开关S1和S2由绝缘操纵杆控制,能同时接“1”或接“2”,向前推操纵杆时轮椅前进且能调速,向后拉操纵杆时轮椅以恒定速度后退.已知蓄电池的电压为24V保持不变,R2的阻值为10Ω,电动机的额定功率为100W,额定电压为24V.请解答下列问题:

上一题 下一题 0.0难度 选择题 更新时间:2017-08-16 08:52:50

答案(点此获取答案解析)

同类题5

阅读理解

    Before I had my son, I spent two years working with children with disabilities. I learnt that shouting and threats of punishment would result in a disaster. Coming up against their behaviour could only make the job harder and their behaviour more extreme. I found something that worked, though.

    There was a very naughty boy in the nursery and a teacher who was generally very confident with the children was asked to take charge of him. One day the boy joined a session in the room next to mine. His appearance created an atmosphere of tension. He spent the entire session running around, hitting and kicking, and destroying property.

    I was in the craft room working with some other children when my co­worker told me that this boy's teacher was in tears, and could not get control of the situation. As we were talking, the boy ran in. I told my co­worker that I would take care of him.

    I closed the door. He was full of energy, throwing things around and making a huge mess. But I could see that he was doing all these to annoy me. He needed connection, and this was the only way he knew how to ask for it. So I sat back down and kept quiet. Then he slowed down and began making a rocket. I talked to him about it. We continued like this for a few minutes before I slipped into the conversation:

    “So what happened today?”

    It was purely a question, no blame or anger in my tone. I believe that if I had criticized him, the gate that was slowly opening would have shut firmly closed. He told me that the teacher didn't let him do what he knew well due to safety but asked him to do what he disliked. He also admitted that he had enjoyed making her run around and saw it as a game. I explained that his teacher had not seen it as a game and was very upset. This again was stated simply as a fact. I suggested that next time he had a session, he talk about what he hoped to do at the start, which might be easier for everyone. He agreed and was quiet for a moment. Then he looked at me with tears in his eyes before quietly asking if he could go to find his teacher to apologize.