问题 问答题

(B)在如图所示电路中,电源内阻不能忽略不计,当变阻器R3的滑动头p由b端向a端移动时,电压表示数______,电流表示数______.(均选填“变小”、“不变”或“变大”)

答案

当滑动变阻器的滑动头p向a端移动时,变阻器接入电路的电阻增大,并联部分电阻增大,外电路总电阻R增大,由闭合电路欧姆定律得知:干路电流I减小,内电压减小,路端电压U=E-Ir增大,即电压表的示数变大.电路中并联部分的电压U=E-I(r+R1)增大,电阻R2的电流增大,电流表的示数IA=I-I2,变小.

故答案为:变大,变小

阅读理解

阅读理解(二)(本题共5小题;每小题2分,满分10分)

阅读下列短文回答问题:

The most unusual museum in London is the Science Museum. In most museums, there’s no shouting and no running, and you aren’t allowed to touch the exhibits. But the Science Museum is different… because it’s noisy ! People talk about what they can see and do there, and some of the machines are noisy as well. Visiting the Science Museum is fun and it’s a great way to learn about science because you can work things out and try out ideas.

When I visit the Science Museum, I go to the Launch Pad. This is my favorite room because you can do physics experiments. For example, if you want to fill a bag with falling sand, you have to move a kind of truck on wheels into the correct position. I also go to the Rocket Show. You can learn how we travel into space and back again.

Then I go upstairs to the Human and Nature room. You can compare your speed with animals there. You hear a noise and push a button. If you aren’t fast enough, the lion catches you! I’m faster than all my friends, but the lion still catches me.

You can do a lot of things in this museum, but you have to obey some rules as well. For example, you mustn’t take photos of the exhibits in the museum. But you can buy postcards of them in the museum shops.

Above all, the Science Museum is free. That means you can drop in for a few minutes or you can stay as long as you like – it’s open every day, from 10 am to 6 pm. So if you ever go to London, make sure you visit the Science Museum. It’s my favorite museum in the whole world.

小题1:Where does Tony go first when he visits the Science Museum?

小题2:What can you try out in the Human and Nature room?

小题3:How much does it cost to go in the Science Museum?

小题4:How long can you stay at the Science Museum ?

小题5:What does the writer think of the Science Museum?

判断题