问题 选择题

已知长直通电导线在其周围某点产生磁场的磁感应强度与该 导线中的电流成正比,与该点到导线的距离成反比。如图所示,a、b、c、d四根长直通电导体棒平行放置,它们的横截 面构成一个正方形,O为正方形中心,a、b、d中电流方向 垂直纸面向里,c中电流方向垂直纸面向外,电流大小满足: Ia=Ic=Id<Ib,则关于a、b、c、d长直通电导线在O点产生合磁场的方向可能是

A.由0点指向aob区域

B.由0点指向boc区域

C.由O点指向cod区域

D.由O点指向aod区域

答案

答案:D

题目分析:由题意及右手定则可知ac导线在O点产生的磁场方向相同,均沿Od方向;导线d在O点的磁场方向沿oc方向,导线b在O点的磁场方向沿oa方向,因为Id<Ib,故导线bd在O点形成的磁场的合场方向沿oa方向,根据平行四边形法则,所以a、b、c、d长直通电导线在O点产生合磁场的方向是由O点指向aod区域,D正确。

单项选择题 A1/A2型题
阅读理解

Societies all over the world name places in similar ways. Quite often there is no official naming ceremony but places tend to be called names as points of reference by people. Then an organized body steps in and gives the place a name. Frequently it happens that a place has two names: One is named by the people and the other by the government. As in many areas, old habitsdied hard, and the place continues to be called by its unofficial name long after the meaning is lost.

Many roads and places in Singapore(新加坡) are named in order that the pioneers will be remembered by future generations. Thus we have names such as Stamford Road and Raffles Place. This is in keeping with traditions in many countries ---- in both the West and the East.

Another way of naming places is naming them after other places. Perhaps they were named to promote friendships between the two places or it could be that the people who used to live there were originally from the places that the roads were named after. The mystery is clearer when we see some of the roads named in former British bases. If you step into Selector Airbase you will see Piccadilly Circus ----obviously named by some homesick Royal Air Force personnel.

Sine places were named after the activities that used to go on at those places. Bras Basah Road is an interesting example, “Base Basah” means “wet rice” in Malay(马来语). Now why would anyone want to name a road “Wet Rice Road”? The reason is simple. During the pioneering days, wet rice was laid out to dry along this road.

A few roads in Singapore are named by their shapes. There is “Circular Road” for one. Other roads may have part of their names to describe their shapes, like “Paya Lebar Crescent”. This road is called a crescent(月牙) because it begins on the main road, makes a crescent and comes back to join the main road again.

小题1:We learn from Paragraph 1 that _____.

A.the government is usually the first to name a place

B.many places tend to have more than one name

C.a ceremony will be held when a place is named

D.people prefer the place names given by the government小题2:What does the underlined phrase “die hard” in Paragraph 1 probably mean?

A.Change suddenly.

B.Change significantly.

C.Disappear mysteriously.

D.Disappear very slowly.小题3:Which of the following places is named after a person?

A.Raffles Place.

B.Selector Airbase.

C.Piccadilly Circus.

D.Paya Lebar Crescent.小题4: Bras Basah Road is named _______.

A.after a person

B.after a place

C.after an activity

D.by its shape小题5:What can be inferred from the passage?

A.Some place names in Singapore are the same as in Britain.

B.Some places in Singapore are named for military purposes.

C.The way Singaporeans name their places is unique.

D.Young Singaporeans have forgotten the pioneers.