题干

(多选)将标有2.5 V 1.25W字样的灯泡和标有20Ω1 A字样的滑动变阻器连接在如图所示的电路中,其中电源电压恒为4.5 V,电流表的量程为0~0.6 A,电压表的量程为0~3 V . 闭合开关,为保证两电表的示数均不超过所选量程,灯泡两端电压不超过额定值(不考虑灯丝电阻随温度的变化),则在变阻器滑片移动的过程中下列说法正确有(      )

A:将变阻器的滑片向右移动,灯泡变亮

B:该灯泡的电阻是5Ω

C:变阻器接入的最小电阻为4Ω

D:灯泡正常发光时,灯泡和变阻器的功率之比为5:4

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答案(点此获取答案解析)

B,C,D

同类题4

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。    

Faces, like fingerprints, are unique. Did you ever wonder how it is possible for us to recognize people?           Yet a very young child – or even an animal, such as a pigeon, can learn to recognize faces. We all take this for granted.

____ When we talk about someone’s personality, we mean the ways in which he or she acts, speaks, thinks and feels that make that individual different from others.

Like the human face, human personality is very complex. But describing someone’s personality in words is somewhat easier than describing his face. ____ ____ But if you were asked to describe a “nice person”, you might begin to think about someone who was kind, considerate, friendly, warm, and so forth.

There are many words to describe how a person thinks, feels and acts. Gordon Airport, an American psychologist, found nearly 18,000 English words characterizing differences in people’s behavior. ____ Bookworms, conservatives, military types – people are described with such terms.

People have always tried to “type” each other. Actors in early Greek drama wore masks to show the audience whether they played the villain’s or the hero’s role. In fact, the words “person” and “personality” come from the Latin persona, meaning “mask”. Today, most television and movie actors do not wear masks. ____

A  If you were asked to describe what a “nice face” look like, you probably would have a difficult time doing so.

B  But we can easily tell the “good guys” from the “bad guys” because the two types differ in appearance as well as in actions.

C  We also tell people apart by how they behave.

D  People have difficulty in describing the features of fingerprints.

E  And many of us use this information as a basis for describing, or typing one`s personality.

F  Experts say that actors differ in their behavioral and physical characteristics in acting.

G  Even a skilled writer probably could not describe all the features that make one face different from another.