某导体两端的电压增大2倍时，通过它的电流（） A．不变 _爱下问搜题

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问题选择题

某导体两端的电压增大2倍时，通过它的电流（　　）

A．不变

B．减小2倍

C．增大2倍

D．无法确定

答案

∵导体的电阻是导体本身的一种性质，电阻大小取决于导体的材料、长度、横截面积，

∴导体两端的电压增大2倍时，导体的电阻不变，

由欧姆定律可知：当R一定时，电流跟电体两端的电压成正比，

∴导体两端的电压增大2倍时，通过它的电流也增大2倍．

故选C．

填空题

根据句子意思，用括号中所给单词的适当形式填空。

1. The tennis player won a gold medal for his coming (twenty) birthday.

2. "I'll do everything I can to help you." She said with a (cheer) voice.

3. (lucky) for me the train was late, so I just catch it.

4. The (explore) of the solar system began in the 19th century.

5. By (use) the Internet you can do your shopping from home.

6. You had better (take) an umbrella-it's going to rain.

判断题

进罐入塔作业前，设备内有毒有害物质的浓度可以略高于装置空气中有毒有害物质的最高允许浓度。