问题 写作题

书面表达。

     周华远在汶川地震灾区的笔友王强失去父母、同学后很伤心,请你以周华的名义写一封信给他,

鼓励他振作起来。

     要求:

     1. 必须用上所有提示词,可适当发挥;

     2. 词数要求:60~80。开头、结尾已给出,不计入总词数。

     提示词:lose one's life, be brave, talk with, get help from, sleep well, 

                   take exercise, relax yourself, smile at life

Dear Wang Qiang,

     I'm sorry to hear that a strong earthquake happened in Wenchuan. ____________________________

_____________________________________________________________________________________

答案

Dear Wang Qiang,

     I'm sorry to hear that a strong earthquake happened in Wenchuan. When I knew that your parents and

some of your classmates lost their lives, I felt very sad. I think you should be brave. You can talk with your

friends or teachers. Maybe you can get help from them. It's also important for you to sleep well. You'd better

take exercise every day. You should learn how to relax yourself. Take good care of yourself and smile at life! 

                                                                                                                                            Yours,

                                                                                                                                           Zhou Hua

答案不唯一

问答题

影响物质材料电阻率的因素很多.一般金属材料的电阻率随温度的升高而增大;半导体材料的电阻率则随温度的升高而减小;

(1)如图(甲)是由某金属材料制成的电阻R随摄氏温度t变化的图象,若用该电阻与电池(电动势E=1.5V,内阻不计)、电流表(量程为5mA、内阻Rg=100Ω)、电阻箱R′串联起来,连接成如图(乙)所示的电路,用该电阻做测温探头,把电流表的电流刻度改为相应的温度刻度,就得到了一个简单的“金属电阻温度计”.

①电流刻度较大处对应的温度刻度值______;(填“较大”或“较小”)

②若电阻箱阻值R′=50Ω,在丙图中空格处(5mA)对应的温度数值为______℃.

(2)PTC元件由于材料的原因有特殊的导电特性,其电阻随温度变化关系复杂.现有一只由PTC元件做成的加热器,实验测出各温度下它的阻值,数据如下:

t/℃0102030405060708090100
R/kΩ1411734568101416
加热器接到200V的电源上,在方格纸上已根据反复实验的大量实验数据作出了PTC加热器功率PR随温度t的变化关系曲线,已知PTC加热器器外表面向四周散热的功率为PQ=0.1(t-t0)瓦,其中t(单位为℃)为加热器的温度,t0为室温(本题取20℃).

①请在同一坐标平面内作出PQ与温度t之间关系的图象

②加热器工作的稳定温度为______℃;

③加热器保持工作稳定温度的原理为:

当温度稍高于稳定温度时:______;

当温度稍低于稳定温度时:______从而保持温度稳定.                        

单项选择题