问题
填空题
白炽灯用久后灯丝变细．灯丝变细是______现象（填物态变化名称）；灯丝变细，电阻变______．
答案
白炽灯用久后灯丝变细．灯丝变细是由固态直接变成气态，是升华现象；钨丝因升华变细，横截面积变小，导致灯丝电阻变大．
故答案为：升华；大．
搜题请搜索小程序“爱下问搜题”
白炽灯用久后灯丝变细．灯丝变细是______现象（填物态变化名称）；灯丝变细，电阻变______．
白炽灯用久后灯丝变细．灯丝变细是由固态直接变成气态，是升华现象；钨丝因升华变细，横截面积变小，导致灯丝电阻变大．
故答案为：升华；大．
If you are writing or studying, it makes much difference where the light comes from. People use 46 and pens every day. They have to be very careful about the way of the light because the light shines on their work. Every 47 gets its light either from daylight 48 the window 49 from the lamps or electricity, 50 no matter what kind of light it is, the way it shines towards our books or work is very important to the eyes. Take a book and sit with your 51 toward the window, and try to read. Your shadow(影子) falls all over the page and makes it 52 for your eyes as if you were in a 53 room. Now turn around and face the window. The page is 54 shadow again, while the bright light is in your eyes. Try sitting with your 55 side toward the window. This is very good for 56 , but if you were writing, the shadow 57 fall across the page and bother you 58 . There is another way – sit 59 your left side to the window. Now everything is perfect for writing as well. Whatever kind of light is in the room, the rule about the right way to sit is 60 the same.
|