问题 选择题

将一根电阻丝接在某恒定电压的电源两端,电流做功的功率为P。若将该电阻丝均匀地拉长为原来的两倍后再接入该电源。则它的功率为 (       )

A.4P

B.0.25P  

C.16P

D.0.125P

答案

答案:B

题目分析:当电阻丝未拉长前,,当电阻丝均匀拉长2倍时,电阻变为,所以电功率变为,B正确;

阅读理解

阅读下面短文并回答问题(请注意问题后的词数要求).

     [1] Do you spend over an hour each day texting messages to your friends? Do you frequently ignore

work, study, and other activities to check your phone for messages? Are you anxious and restless if you

are separated from your mobile phone? Do you hardly ever use your phone to talk any more , and do

your thumbs hurt from texting too much?

    [2] lf_________ , then it is very possible that you are a textaholic. A textaholic can be defined as

someone who is addicted to sending and receiving messages. The main symptoms are a strong

desire to text messages, which takes precedence  (优先)  over everything else. And bad moods, low

spirits and a lack of self-confidence if messages fail to come in. The root of the problem, as

with many addictions, is the desire to escape from emotional difficulties such as stress , anxiety and

relationship problems. Expercs warn that text addiction is likely to become the most common form of

addiction in the future , especially among the young.

    [3] So what can you do if you think you may be a textaholic? The key is to get your life back in

balance. Make sure your resist the urge to answer every message you receive, and consider leaving your

mobile phone behind occasionally when you go out. Most importantly,make a point of spending quality

time with friends and family , and make time to re-learn the art of face-to-face conversation instead of

conducting your relationships by means of text messages. Not only will you save time add money, but

you may also rediscover the pleasure of true communication.

1. How does the author introduce the topic of the text?

  ( no more than 5 words)

__________________________________________________________

2. Fill in the blank in Paragraph 2 with proper words.

  ( no more than 8 words)

___________________________________________________________

3. What emotional difficulties may be the causes of text addiction?

  ( no more than 5 words)

①_____________②______________③____________

4. What do experts say about text addiction?

  ( no more than 14 words)

___________________________________________________________

5. What is the main idea of Paragraph 3?

  ( no more than 8 words)

____________________________________________________________

问答题 简答题