问题 填空题

加在一段导体两端的电压是6V时,导体中的电流为2A;若要使通过该导体的电流变为0.5A,则导体两端所加电压应为______V;若该导体两端所加电压为零,则其阻值______Ω.

答案

由欧姆定律可得:

导体两端的电阻R=

U
I
=
6V
2A
=3Ω;

要使电流变为0.5A,则所加电压U′=I′R=0.5A×3Ω=1.5V;

导体的电阻与导体两端是否有电压无关,故电压为零,其阻值仍为3Ω;

故答案为:1.5;3.

阅读理解

A little knowledge can make a difference at a time of life or death. Do you know what to do if you find yourself in an earthquake?

lf you are inside:

Quickly move under a strong desk, a strong table or along a wall. You can also go into a small room like the bathroom. This will protect you from falling things. Do not get into a lift.

Don't stand near windows, large mirrors, heavy furniture of fireplaces.

If you're outside:

Move away from buildings and streetlights. These could fall on you. Squat(蹲下) and protect your head until the shaking stops.

After the earthquake:

Check, take care of injuries and help make sure people around you are all right. Watch out for aftershocks.

Protect yourself by wearing long pants, a long-sleeved(长袖的)shirt and strong shoes. Listen to tile radio for the latest information.

小题1:If you are in a tall building when an earthquake happens, you'd better        .

A.run into a lift

B.not stay in the bathroom

C.stand near large mirrors

D.not stand near windows小题2:lf you outside during an earthquake        

A.you must move into a building

B.you cannot squat

C.you have to stop the shaking

D.you must move away from streetlights小题3:After the earthcluake, you should        

A.look after injuries

B.not help the others around you

C.protect yourself without wearing shoes

D.not listen to the radio for the latest information小题4:The underlined word "aftershocks" in the passage means        in Chinese.

A.震感

B.震源

C.余震

D.防震

单项选择题