题干

如图所示,是电学实验中常用的滑动变阻器,其作用除保护电路外,还能改变电路中的电流和电压,关于滑动变阻器的作用,下列说法不正确的是(     )

A:在探究“电流与电压关系”的实验中,其主要作用是改变电压,多次测量,得出普遍规律

B:在“测量未知定值电阻Rx的阻值”的实验中,其主要作用是为了多次侧量,求平均值

C:在探究“电流与电阻关系”的实验中,其主要作用是保持R两端的电压不变,便于多次测量,得出普遍规律

D:在“测量小灯泡电阻”的实验中,其主要作用是为了多次测量求平均值,减小误差

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答案(点此获取答案解析)

D

同类题2

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    I was diagnosed with allergies (过敏反应) when I was a little kid. Other than family, no one truly knows I have allergies, although I have to tell people it's allergies when my eyes start to tear up. ____ Sometimes my friends just tease in a friendly way.

    ____I look like a normal kid. I don't mind telling people about my allergies—after all, it's normal to have them. Having allergies hasn't affected my self-confidence.

    ____For example, I am a big traveler and I would enjoy going to see the cherry blossoms in Washington, D. C. But when I come anywhere within a 10-foot range of cherry blossoms it feels like I lose almost all my senses! Even though it's only temporary, I still feel miserable.

    My allergies haven't stopped me from traveling when I can, though. My class trip was to Williamsburg in Virginia. At first it was supposed to be during cherry blossom time, and that had me worried. ____

    I've had to rethink some of my dreams, too. Since I'm allergic to animals with fur, I may need to adjust my hopes of being a veterinarian (兽医) or working in an agricultural-science department. ____

    Now I have learned to deal with my allergies and even see the good side sometimes. Having allergies has taught me not to be prejudiced about people's health conditions.

A. I do get made fun of.

B. My allergies have been getting better.

C. If I don't take my medicine I can get really bad breath.

D. You can't tell by looking at me that I have a health condition.

E. Fortunately, it was changed to February, so I went and had the best time!

F. But I'm interested in so many things and there are plenty of other careers out there!

G. Sure, my allergies have held me back from doing some of the things that I love to do.