如圖所示電路,電阻R
1=R
2=4Ω,電源電壓保持不變,當(dāng)S
1、S
2都閉合時(shí),電流表的示數(shù)為0.75A,此時(shí)電路是______聯(lián)電路,電路的總電阻是______Ω;當(dāng)S
1閉合、S
2斷開(kāi)時(shí),電路的總電阻是______Ω,電流表的示數(shù)是______A.
![](http://hiphotos.baidu.com/zhidao/pic/item/fcfaaf51f3deb48f237f746af31f3a292df57874.jpg)
當(dāng)S
1、S
2都閉合時(shí),兩電阻并聯(lián)在電路中.
R=
==2Ω電源電壓:U=IR=0.75A×4Ω=3V
當(dāng)S
1閉合、S
2斷開(kāi)時(shí),電路的總電阻是R
1的電阻4Ω
I=
==0.75A故答案為:并,2Ω,4Ω,0.75A.