7．按同样的方法，找出其余4个基准点的4组等电势点．

6．按步骤5的方法在这个基准点两侧逐步由近及远地各探测得到5个等电势点．

5．接通电源，将一探针跟AB连线上某一基准点相接触，然后在导电纸平面AB连线旁距此基准点约lcm处轻轻移动探针，直到使电流表指针不再发生偏转．用探针把这一点位置复印在白纸上．

4．在导电纸上画两个电极的连线AB，在连线上取大致相等的5个点作基准点，并用探针把它们的位置复印在白纸上．

3．将两根探针分别接到电流表的“+”、“一”接线柱上（如图1-1所示）．

2．在导电纸上相距8―l0cm，平放两个圆柱形电极（或用两枚图钉代替），并将电极分别与6V直流电源的正负极相连接．

1．在平整的木板上，由下而上依次铺放白纸、复写纸、导电纸各一张，导电纸应将导电面朝上，用图钉把三层纸一起固定在木板上．

学生用低压电源或电池组、灵敏电流计、开关、导电纸、白纸、复写纸、圆柱形金属电极两个、探针两支、图钉、导线若干、木板和塑料底板．

实验步骤

答案

œ【书面表达练习1】

Dear Mrs Brown,

We are so glad that you're coming to join us on Saturday. Here is how you can find us. We'll have our gathering party in the Central Park. Maybe you've been there, haven't you?

Go straight on when you get out of the school gate and come to the street. Then turn right at the second crossing and you'll find a hospital. Just opposite it is a No. 7 bus stop. Take a bus and get off at the fourth stop. Central Park is just in front of it. We'll have our gathering party in a boat on the lake. What a funny thing! Do come on time. We'll wait for you at the park gate.

                                                                              Yours,

                                                                           Li Hong

œ【书面表达练习2】

April 9^th, 2003

Dear Jim,

Our friend Li Ming will leave for Shanghai to study. So we are going to have a get-together at 3:30 this Friday afternoon. He lives at No.225 Dongfeng Street. It is not very difficult to find your way to his home. Take a No.2 bus, the stop of which is on the left of your university, and get off at the second crossing. There is a cinema across the street. Turn right at the corner, and you will find Dongfeng Street. Li Ming’s home is 200 yards down the street on the right. There is a post office opposite to Li Ming’s home.

                                Yours,

                                Zhang Hua

这是一篇图画说明文，根据图画，指明路线，如何到达中心公园。注意观察图画，确定出发点、行走路线、目的地，灵活使用表达路线的表达语。

Dear Mrs Brown,

We are so glad that you're coming to join us on Saturday. Here is how you can find us. ___________________________________________________

______________________________________________________________________________________________________________________________________________________________________________________________________

Yours, Li Hong

œ【书面表达练习2】

假定你叫张华，你的同学李明即将去上海学习。现由你写一封便函给你们的朋友Jim，约他聚会。内容要点如下：

（1）聚会时间：本星期五下午3点30分；

（2）聚会地点：东风路225号，李明家。

（3）按下图所画路线告诉Jim怎样去李明家。

注意：

（1）便函用英语写，并注明便函的时间：2003年4月9日；

（2）内容包括说明部分和要点；

（3）字数：80－120。