问题 问答题 论述题

利用载体催化元件测量瓦斯浓度的原理。

答案

参考答案:

设催化元件r1(黑元件)作为工作元件,r2(白元件)作为补偿元件。无瓦斯时,测量电桥电路处于平衡状态,r1与r2中流过相同的恒定电流;当有瓦斯时,瓦斯与氧气在工作元件表面起反应,从而引起元件电阻增加,导致电桥失去平衡,产生一个与瓦斯浓度成正比的输出电压信号,测出此信号的大小即得瓦斯浓度的高低。

填空题
阅读理解

What makes a gift special? Is it the price you see on the gift receipt? Or is it the look on the recipient's face when they receive it that determines the true value? What gift is worth the most?

This Christmas I was debating what to give my father. My dad is a hard person to buy for because he never wants anything. I pulled out my phone to read a text message from my mom saying that we were leaving for Christmas shopping for him when I came across a message on my phone that I had locked. The message was from my father. My eyes fell on a photo of a flower taken in Wyoming. and underneath a poem by William Blake. The flower, a lone dandelion standing against the bright blue sky, inspired me. My dad had been reciting those words to me since I was a kid. That may even be the reason why I love writing. I decided that those words would be my gift to my father.

I called back. I told my mom to go without me and that I already created my gift. I sent the photo of the cream-colored flower to my computer and typed the poem on top of it. As I was arranging the details another poem came to mind. The poem was written by Edgar Allan Poe; my dad recited it as much as he did the other. I typed that out as well and searched online for a background to the words of it. The poem was focused around dreaming, and after searching I found the perfect picture. The image was painted with blues and greens and purples, twisting together to create the theme and wonder of a dream. As I watched both poems passing through the printer, the white paper coloring with words that shaped my childhood. I felt that this was a gift that my father would truly appreciate.

Christmas soon arrived. The minute I saw the look on my dad's face as he unwrapped those swirling black letters carefully placed in a cheap frame, I knew I had given the perfect gift.

小题1:The idea for a special gift began to form when the author was______.

A.doing shopping

B.having a debate

C.reading a message

D.leaving for Wyoming小题2:The author's inspiration for the gift came from_____.

A.a photo of a flower

B.a story about a kid

C.a call from the mother

D.a text about Christmas小题3:The underlined word "it" in Paragraph 3 refers to a poem by_____.

A.the father

B.the author

C.William Blake

D.Edgar Allan Poe小题4:The author made the gift by_____.

A.searching for the poems online

B.drawing the background by hand

C.painting the letters in three colors

D.matching the words with pictures小题5:What is the main purpose of the passage?

A.To show how to design images for gifts.

B.To suggest making gifts from one's heart.

C.To explain how computers help create gifts.

D.To describe the gifts the author has received