题目

如图所示电路，电源电压6V保持不变，定值电阻R1=10Ω，滑动变阻器R2的最大阻值为20Ω．闭合开关，在滑片b端向a端移动的过程中，以下说法正确的是 A. 滑片在b端时，电流表示数为0.3A B. 滑片移到中点时，电压表示数为2VC. 电路消耗的最大功率为3.6W D. 电压表示数与电流表示数的比值不变 答案：【答案】C【解析】A. 滑片在b端时，定值电阻与滑动变阻器串联，则I＝＝0.2A，故A错误；B. 当滑片移到中点时,则此时电路中的总阻值R′＝R1+R2＝10Ω+12×20Ω＝20Ω，则电流I′＝ ＝0.3A，由I＝得：电压表示数UV＝I×+R2＝0.3A××20Ω＝3V；故B错误；C. 当滑片移到a端时,滑动变阻器接入电路的阻值为零,只有R1连入电阅读理解。     Critical thinking is an important skill that can increase students' ability to learn in any situation. This can be applied to traditional education, online education, or directly in a career related role. Many teachers find it such a valuable skill that they give their students a critical thinking question every day. Developing this ability can mean the difference between "just passing a course" and "understanding the material well enough" so that what students learn from it will follow them throughout their life.      Some characteristics of a critical thinker that teachers should encourage are:      -asking questions as a reaction to something read or discussed;      -determining the "deeper meaning" of a particular passage or topic;      -providing input and opinions to topics as a direct result of analysis and research;      -reasoning in an effort to develop an argument of your own opinion.     It is important for a student to understand more than definition (定义). One way to truly understand an idea is to have hands-on practice, and to apply concepts learned in a textbook. Such "mini-examples" will interest a student and improve their understanding of a topic. This is how lifelong skills can be developed.     Teachers that use critical thinking practices in the classroom can "go above and beyond" by asking questions that promote a greater comprehension of the material. Instructors should be able to challenge students and create an environment where they are analysing material and gaining a better understanding. This will make the classroom move in a direction for learning. It can also help students to stay interested in the course material, as they always have a new concept to consider.      At the same time, students benefit greatly from developing critical thinking skills. When learned early on, these skills can be used throughout their college education. Students can understand how to consider a topic, analyse it, and discuss it from different points of view. These are skills that will benefit them when they are part of the workforce as well. 1. Critical thinking can best be described as _____.  A. a system to improve people's memory B. a method to expand people's knowledge C. a way to increase people's ability to understand D. a process to make people more critical of others 2. The underlined word "it" in Paragraph l refers to _____. A. the ability B. the difference C. the course D. the material 3. According to the passage, a critical thinker should _____. A. ask questions before reading the material B. be able to develop their own opinions C. predict the deeper meaning of a topic D. do more analysis and research 4. The author thinks "mini-examples" are useful because they _____. A. assist students to better remember definitions B. give students hands-on practice C. help to keep students interested D. help students develop concepts5. Who are the intended readers of the passage? A. Teachers. B. Parents. C. Examiners. D. Headmasters.