问题 计算题

如图中电源电动势E=10 V,内阻可忽略,R1=R2=5 Ω,C=30 μF,求:

(1)S闭合稳定后通过R1的电流;

(2)S原来闭合,然后断开,求这个过程中流过R1的总电荷量。

答案

(1)I1="1A"

(2)ΔQ=1.5ⅹ10-4C

(1)闭合稳定后,有闭合电路欧姆定律得

I1=E/(R1+R2)=1A    (3分)

(2)闭合时,电容器两端电压为U1=I1R2=5V     (2分)

断开后,电容器两端电压为U2=E=10V    (2分)

两次电容器所带电荷量之差为ΔQ=C(U2-U1)=1.5ⅹ10-4C    (2分)

阅读理解

根据短文内容,判断正(T)误(F)。

    In general, people talk about two groups of colors: warm colors and cool colors. Scientists think that there

are also two groups of people: people who prefer warm colors and people who prefer cool colors.

    The warm colors are red, orange and yellow. Where there are warm colors and a lot of light, people usually

want to be active. People think that what red symbolizes (代表) is exciting sociable (善交际的) people who

like to be with others like red. The cool colors are green, blue and purple. These colors unlike warm colors,

are relaxing. Where there are cool colors, people there are usually quiet. People who like to spend time alone

often prefer blue.

     Red may be exciting but one scientist says that time seems to pass more slow in a room with warm colors

than in a room with cool colors. He suggested that a warm color such as red or orange, is a good color for a

living room or a restaurant. People who are relaxing or eating don't want time to pass quickly.

     Cool colors are better for offices or factories as the people who work there want time to pass quickly.

Scientist don't know why people think some colors are warm and other colors are cool.

     However, almost everyone agree that warm colors remind people of warm days and cool colors remind

them of cool days. Because in the north the sun is low during winter, the sunlight appears quite blue. Because

it is higher during summer, the hot summer sunlight appears yellow.

( )1. When people talk about two groups of people, they mean those that like warm colors and like cool

           colors.

(     )2. The warm colors are red, purple and yellow.

(     )3. The people who like warm colors are very easy to get on with others.

(     )4. The persons who are relaxing don't want time to pass slowly.

(     )5. The best title of the passage is "Colors and People".

填空题