题干

如图所示,一理想变压器给一标有“20V,10W”的小灯泡供电,原副线圈分别接一理想电流表和一理想电压表。当原线圈输入220V的交变电流时,闭合开关S小灯泡恰好正常发光。下列说法正确的是(   )

A:变压器原、副线圈的匝数比为1∶11

B:变压器原、副线圈中每匝线圈的磁通量的变化率之比为11∶1

C:将开关断开,电压表的示数将为0

D:灯泡两端再并联一盏相同的灯泡,电流表的示数将变为原来的两倍

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答案(点此获取答案解析)

D

同类题1

根据短文内容,选择适当的单词或短语填空,使短文意思完整。每个选项仅使用一次。

A. ride to the gym   B. because   C. keeping fit   D. so  E. cheer me up

F. enjoy my day off   G. healthier   H. also   I. funny   J. coughing and sneezing

Hi Jake,

    How's it going? Sorry I haven't been in touch for a while, but couldn't use my computer for a few days. You'll never guess what happened to me!

    A couple of weeks ago, I decided to take up yoga. Yoga is a combination of physical and breathing exercises. It's supposed to be good for relaxation and ____. I've been feeling a bit stressed about my school work recently and I thought yoga might help.

    My dad couldn't give me a lift to the first lesson, so I decided to ____. The lesson was great and I felt really relaxed afterwards. On the way home, though, it started raining and I got very wet! The next day, I woke up with a bad cold. I couldn't stop ____.

    I couldn't go to school ____I also had a high temperature. We were having a math test that day so it was great that I could stay at home. I didn't really ____, though. I felt awful and stayed in bed. Mum brought me cups of hot tea for my sore throat(and you know how much I hate tea! ). She ____went to the chemist's and got me some vitamin pills. I have to keep taking these for a while ____I can get stronger.

    That afternoon Robbie came to visit me. He said he'd got something to ____and pretended it was the math test that I'd missed "Mr Bank says you can do it at home instead,” he said, but I knew he was joking. I didn't think it was very ____, but he did!

    The next day, I was still a bit pale and didn't have much energy, but I was feeling better. The day after that, I was able to go back to school.

    Can you believe my luck? I went to the yoga class to feel ____and instead I caught a cold!

    Anyway, I hope you're OK. Write and let me know what you've been up to!

    Bye for now!

Kate

同类题5

完形填空,阅读下面短文,然后从各题所给的四个选项中选出一个最佳答案。

    Once there lived two brothers. The elder was called Simon and the younger Victor. They1each other very much, and always took care of one another. Every day they worked from morning2night, getting as much grain(谷物) as possible from their fields.

    One late autumn evening, after their work in the3was done, Simon said to his wife, "Victor got married last month. He has many bills(账单) to pay. I think I will put a bag of rice in his barn(谷仓). “Oh, that's a good idea,” said his wife. “But please don't tell him,” said Simon, “If he knows I put the rice there, he will4take it.”

    So, late that night Simon took a bag of rice to Victor's barn. The next day, while looking at his own barn, he found5strange. “I took a bag of rice to Victor's house last night,6I still have the same number of bags in my barn.7did that happen?”

    Simon decided to take another bag of rice to his brother's barn that night. But the next morning, he found the8number of bags in his barn again! “This is very strange,” he thought. That night he9again. He carried a large bag of rice on his shoulder(肩膀); and walked down the road to his younger brother's house. In the bright moonlight, he could see another10coming down the road. He was carrying something on his11, too. “Younger Brother!” Simon cried, “What are you doing?” “I was 12you, Older Brother,” said Victor, “Your family is13than mine. I thought you needed more rice.” The two brothers quickly14that they had been taking rice to each other. They15what had happened. “It is good to have a brother like you,” they both said. And they lived happily ever after.