题目

某时刻LC回路中电容器中的电场方向和线圈中的磁场方向如图14-2-19所示.则这时电容器正在_____________（充电还是放电），电流大小正在_____________（增大还是减小）. 图14-2-19 答案：解析：用安培定则可知回路中的电流方向为逆时针方向，而上极板是正极板，所以这时电容器正在充电；因为充电过程电场能增大，所以磁场能减少，电流在减小.答案：充电     减小It took firemen almost an hour to cut through the wreckage (残骸) of the car. By the time they reached the driver，Wong，he had died. Seconds before the crash happened, the traffic on the road was flowing smoothly，and Wong was an experienced driver in a sturdy car. What could have caused the tragedy? Alcohol. After Wong had drunk four cans of beer, his physical and mental reactions had slowed. He had a false feeling of confidence. Then he lost control, hitting a fire hydrant and a lamp post. In almost every other developed country, Wong might have thought twice about getting behind the wheel and setting off in his car after drinking beer. His passengers might have refused to join him. Would you fly with a drunk pilot? Laws and public campaigns against drink-driving in many countries have changed people's lifestyles and saved thousands of lives. Drink-drivers are regarded as potential killers. In some countries, police on roadsides pull over motorists and check whether they have been drinking or not. In 1995, about 7 % of drivers killed in road accidents in Hong Kong were drink-driving. But this does not tell us the full extent of the problem because it does not show the number of motorists and pedestrians (行人) killed by drink?? drivers who survived their crash. In reality then, the number of people killed as a result of drink-driving must be much higher. But in 1995, only five people were prosecuted (起诉) for being drunk and incapable of controlling a vehicle. Mr . Wong crashed his car because __________. A. he had been drinking beer        B. his car was faulty C. he did not sleep                D.he was not a very good driver The underlined sentence" Would you fly with a drunk pilot?" questions whether we would_____________. A. stay with a person we dislike           B. fly on a plane if we were drunk C. do something obviously dangerous      D.be brave enough to risk our lives According to paragraph 3, which of the following statements is correct? A. In 1995 at least 7% of drivers killed in road accidents in Hong Kong were drink-driving.ks.5u B. Drink-driving is getting worse and worse in Hong Kong. C. Most drink-drivers survive their crash. D. The number of pedestrians killed is larger than the number of drivers killed.