问题 填空题

某同学在用电流表和电压表测电池的电动势和内阻的实验中,串联了一只2.5Ω的保护电阻R0,实验电路如图所示,

(1)连好电路后,当该同学闭合电键,发现电流表示数为0,电压表示数不为0。检查各接线柱均未接错,接触良好且未发生短路;他用多用电表的电压档检查电路,把两表笔分别接a、b,b、c,d、e时,示数均为0,把两表笔接c、d时,示数与电压表示数相同,由此可推断故障是         

(2)排除故障后,该同学顺利完成实验,根据数据在U—I图中描出图线,由图知:电池的电动势为       ,内阻为        

答案

(1)R断路(2分)

(2)1.42~1.50V   0.2~0.4Ω

(1)闭合电键,发现电流表示数为0,电压表示数不为0,说明电路中有断路或者短路的地方,把两表笔接c、d时,示数与电压表示数相同,则c、d点通往电源的电路是通路,即R断路

(2)根据闭合电路欧姆定律可得,U=E-I(r+R),则图线斜率表示内阻,纵截距表示电源电动势,跟据图像可知电动势为1.42V,内阻

故答案为:(1)R断路(2)1.42~1.50V   0.2~0.4Ω

阅读理解

阅读理解。

     Lots of people like diving into water, because they can explore the underwater world. But there is not

her kind of diving. Some people dive into the sky! This is really a very exciting sport. A skydiver goes high up in the air on a plane. Then he jumps off the r)lane and floats in the air with the help of a parachute(降落伞). A parachute is like a huge umbrella. It is put on the back of the skydiver. When the skydiver reaches a certain height, he will pull a string and the parachute will open up in seconds and carry him gently down

to the ground. Skydivers like doing a lot of fascinate tricks in the air. After jumping off the plane one after

another, they will try to stay in the air and hold each other's hands. They can form different shapes.

     Is it safe to do skydiving?Yes, as long as we receive right training.But sometimes, accidents do happen. In Canada, two skydivers were killed in 1991 when they jumped off the plane. Because their parachutes

got tied up with each other, the parachutes couldn't open up and both crashed down and died.

1. Why do people like diving into water?

                                                                    

2. How does a skydiver go up into the sky?

                                                                    

3. What does a parachute look like?

                                                                    

4. Where does a skydiver put his parachute?

                                                                    

5. Why were two skydivers killed in Canada?

                                                                    

6. What do you think of skydiving?

                                                                         

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