问题 问答题

传感器担负着信息的采集任务,在自动控制中发挥着重要作用,传感器能够将感受到的物理量(如温度、光、声等)转换成便于测量的量(通常是电学量),例如热敏传感器,主要是应用了半导体材料制成的热敏电阻将热学量转换为电学量.热敏电阻随温度变化的图象如图甲所示,图乙是由热敏电阻R1作为传感器制作的简单自动报警器线路图.问:

(1)为了使温度过高时报警器铃响,c应接在______(填“a”或“b”).

(2)若使启动报警的温度提高些,应将滑动变阻器滑片P点向______移动(填“左”或“右”).

(3)如果在调试报警器达到最低报警温度时,无论如何调节滑动变阻器滑片P都不能使报警器工作,且电路连接完好,各电路元件都能处于工作状态,则造成工作电路实际不能工作的原因可能是______.

答案

(1)根据图甲坐标系中曲线的趋势可以得出,电阻随温度的升高而减小,因此热敏电阻的阻值随温度的升高而减小,为了使温度过高时发送报警信息,则热敏电阻阻值最小,开关c应该接在a处,

(2)若使报警的最低温度提高些电路中电阻增大,则滑动变阻R应将P点向左移动.

(3)在最低报警温度时不能报警,说明此时电路中产生的电流不能让竖直片与a接触,这可能由多种原因造成,如:①电源提供的电流太小,导致磁铁的磁性太弱;②弹簧的劲度系数太大,电磁铁的吸引力小于弹力等

故答案:(1)a (2)左;(3)①电源提供的电流太小,导致磁铁的磁性太弱;②弹簧的劲度系数太大,电磁铁的吸引力小于弹力等

阅读理解

任务型阅读:根据短文内容完成下列句子

       I asked Mom to let me cook dinner for the family last night. I told her I'd cook something simple so

she agreed.

       We usually eat Asian food like Chinese or Japanese, but I decided to make something different. I

chose an Italian food-Spaghetti with meat sauce(肉羹).Spaghetti is easy to cook.

       I put enough Spaghetti for everyone in my family into a pot of boiling, salted water. I let it cook for

about ten minutes. But before this, I made the meat sauce.

       I want the meat sauce to be really delicious. I chopped(剁碎)an onion into small pieces. I fried the

onion in the oil for a few minutes.

       When the onion was soft, I put some beef into the pot with the onions, and fried them together for a

few minutes. Then I added some tomatoes. Finally, I added some tomato juice and let it cook on a low

heat for about an hour.

       When the Spaghetti was ready, I put it into a large bowl. Then l poured the meat sauce over it.

       There was enough for everyone and we all put some cheese on top of it.  Everyone enjoyed it and

Mom said she would let me cook something else another day.

       I'm going to read a cook book and find something really interesting to cook.

1. I want to cook something ________for my family.

2. We usually eat _________food, but I decided to choose an _________food-Spaghetti.

3. I add some _________,beef into the meat sauce and it must be_________.

4. After frying beef with the onions together for a few minutes, I again added some_________.

5. Everyone in my family enjoyed the meal and I'm going to read a ________to find something

really ________to cook.

填空题