问题 选择题
如图所示,处在磁感应强度为B的匀强磁场中的单匝矩线圈abcd,以恒定的角速度ω绕ab边转动,磁场方向垂直于纸面向里,线圈所围面积为S,线圈导线的总电阻为R.t=0时刻线圈平面与纸面重合,且cd边正在离开纸面向外运动.则正确的是(  )

A.时刻t线圈中电流的瞬时值icosωt

B.线圈中电流的有效值I

C.线圈中电流的有效值I=

D.线圈消耗的电功率P

答案

答案:C

完形填空

Using a Mobile Phone to Improve Mother and Child Health

People around the world are working to expand the uses for mobile technology in health care.

In the world, there are six billion mobile phone users in a population of seven billion people.

   小题1:     Africa has widespread adoption. Three or four years ago the penetration rates were 20 percent or 30 percent, and now they’re getting upwards of 60 percent in some countries.

    小题2:     Earlier research has been to look at mobile technologies and HIV and AIDS. And so we have some great evidence on the effectiveness of mobiles.

During the first week of December, 2012, more than 4,000 people from 50 countries met for the fourth annual mHealth Summit. It brought together experts from what the organizers call the mHealth ecosystem.

In 2011 Secretary of State Hillary Clinton started a public/private partnership called the Mobile Alliance for Maternal Action, or MAMA. There are about 800 women a day and about three million babies a year die from pregnancy and childbirth-related causes.      小题3:     The messages cover pregnancy and the first year of a baby’s life. These health messages may also be sent to a pregnant woman’s husband and mother-in-law.    小题4:    

Messages can be text or voicemail. You can have a pregnant woman in Bangladesh registered into a system that provides messages that help her know what to do and when to do certain things.

Simple text messages can be important sources of information to people without Internet

access.      小题5:     They have to be able to read through thousands of entries that come back to them on Google, for example, and then figure out what that information means to them. And that’s not something that someone in a poor and uneducated kind of situation can do.  

A.They have no access to the relevant information.

B.That way they too can understand what needs to be done.

C.Millions of messages about baby care are received every day.

D.A lot of work has been done to use mobile technology for health.E. And the most rapidly growing markets are those in developing countries.

F. The program sends messages to women to educate them about their health.

G. Besides, online users may sometimes not understand all the information available.

单项选择题