题干

物理学研究中常常用到“控制变量法”、“等效法”、“类比法”等科学方法。在下列研究实例中运用了控制变量法的是(    )

A:研究电流的形成原因时将电流与水流比较从分析水流的形成入手来分析电流的形成

B:研究电流的大小时根据电流产生的效应大小来判断电流的大小

C:研究多个电阻组成的电路时求出电路的总电阻用总电阻产生的效果来代替所有电阻产生的总效果

D:研究电流与电压的大小关系时保持电阻大小不变改变电阻两端的电压值观察电流如何随电压变化而变化

上一题 下一题 0.0难度 选择题 更新时间:2018-10-08 11:46:56

答案(点此获取答案解析)

D

同类题5

读下面短文,按照句子的语法情况和上下文连贯的要求,在空白处填入适当的词或用括号中所给词的正确形式填空。每空不超过两词。

    Florence Nightingale was a nurse who saved many people in the 19th cenury. She was named after the city of Florence in Italy.

    Florence was ____ unusual young woman for her time, bemuse she didn't want to go to parties and get married. She wanted to be a nurse and help people. Her family ____ (not)want her to become a nurse because hospitals back then were dirty, horrible places.

    ____ the age of thirty-one, Florence went to Germany and learned all about nursing. It was hard work, ____ she loved it.

    In 1854, lots of British soldiers went to fight in the Crimean War. Army hospitals were filled with injured people, but there ____ (be)no nurses and many soldiers died. Florence and a team of nurses went to help.

    Florence worked 20 hours a day to make the hospital ____(clean)and safer place. She brought fresh food, she cleaned the beds and she used clean bandages on the wounded soldiers fewer ____ (man) were dying.

    At night, Florence talked to the injured soldiers and helped them ____(write) letters to their families. They called her "the lady with the lamp", ____ she always carried a lamp.

    When Florence returned to England, people called her a hero. Queen Victoria wrote her a letter to say thanks, She ____ (give)the honor(荣誉)----Order of Merit, becoming the first woman to receive it