问题
填空题
如图，已知R1=4Ω，R2=2Ω．当开关S断开时，电流表示数为2A，则开关S闭合时，电流表示数为______A，R2两端电压为______V．
答案
当开关S断开时，U=I（R1+R2）=2A×（4Ω+2Ω）=12V
当开关S闭合时R2被短路，U2=0，I′=
=U R1
=3A12V 4Ω
故答案为：3，0
搜题请搜索小程序“爱下问搜题”
如图，已知R1=4Ω，R2=2Ω．当开关S断开时，电流表示数为2A，则开关S闭合时，电流表示数为______A，R2两端电压为______V．
当开关S断开时，U=I（R1+R2）=2A×（4Ω+2Ω）=12V
当开关S闭合时R2被短路，U2=0，I′=
=U R1
=3A12V 4Ω
故答案为：3，0
选择适当的词（组）并用适当形式完成短文。每个词（组）只使用一次，其中有两个词（组）是多余的。
We see animals, like rabbits, bees, dogs, birds, 小题1: …, but do you know how these animals 小题2: things? First, let’s see a rabbit. When a rabbit sees something 小题3: , it runs away at once. When it runs, its tail 小题4: up and down. When others see this, they run away, too. Many other animals use this kind of way. When a bee finds some food, it goes back to ____小题5:_ home. It can’t tell the ___小题6:_____bees where the food is by speaking to them, but it does a little dance in the air. This may _小题7:_____ other bees where the food is. Some animals say things by ___小题8:_____ sounds like a man does. For example, a dog barks when a ___小题9:___comes near. Some birds can make several different sounds, each with its own __小题10:___-. In a word, every animal has its own language. |