问题 填空题

电火花计时器工作电源是220V的______电源(填“直流”或“交流”).现在使用打点计时器测定物体的速度,当电源频率低于50Hz时,若仍按照50Hz计算,则测出的速度值将比真实值偏______(选填“大”或者“小”)

答案

电火花打点计时器是使用220V交流电源的仪器,其打点周期与交流电的周期相同,若交流电频率为50赫兹,则其打点周期为0.02s,当电源频率低于低于50Hz时,实际打点周期将变大,而进行计算时,仍然用0.02s,因此测出的速度数值将比物体的真实数值大.

故答案为:交流,大.

阅读理解

B

Home schooling offers other unforeseen advantages as well. One of these might be more available time. Home schooling can be an effective way to teach. The time you have during the day can be used resourcefully, in this manner reducing the overall time that the student in fact spends at school.

Home schooling allows the parent to develop into the main adviser and foundation of guidance for a child. This connection could be the basis of a higher degree of trust between the child and the parent where the child is more apt to come to the parent for help and direction as an alternative of turning somewhere else.

Home schooling can be an instrument for a special case where a child may have been a target of extreme harassment(侵扰)at a standard public school. way to re-focus on learning and makes the child be able to receive the close parental leadership.

It is a proven fact that home schooled students do well when it comes to college preparation. In addition, it is a fact that home schooled students can do as well as their public schooled peers in college.

Home schooling is not for every person. Each parent should cautiously assess . There are many considerations to be made when choosing home schooling, but for many, home schooling has been a preference that has proven to be very beneficial to the student’s exceptional education.

45. The passage mainly talks about _______.

A. how to carry out home schooling

B. the advantages of home schooling

C. home schooling and standard public schooling

D. parents’ preference for home schooling

46. A student trapped in school harassment may not _______.

A. focus his / her attention on learning

B. get along well with others

C. form a good habit of learning

D. form a tight connection with his / her teacher

47. The college and SAT assessments are referred in this passage to prove that _______.

A. the final results of home schooling are doubtful

B. public schooled students do better than home schooled students

C. home schooling is equal to or better than public schooling

D. home schooling may not be beneficial to every person

48. Which of the following may the writer agree with ?

A. Home schooling has more advantages than disadvantages

B. Parents should devote their time to home schooling

C. Home schooling is usually not as effective as expected

D. Many factors should be considered before choosing home schooling

填空题