電阻器在電路(lu)中起什么(me)作用呢？

將電(dian)(dian)(dian)路中的開關換(huan)為1個470歐姆(mu)的電(dian)(dian)(dian)位器(qi)。旋轉電(dian)(dian)(dian)位器(qi)的轉柄，小(xiao)燈泡(pao)的亮(liang)度要隨著電(dian)(dian)(dian)阻值(zhi)(zhi)的大小(xiao)而(er)改變(bian)。電(dian)(dian)(dian)阻值(zhi)(zhi)越(yue)大，小(xiao)燈泡(pao)越(yue)暗。這說(shuo)明(ming)電(dian)(dian)(dian)阻器(qi)在電(dian)(dian)(dian)路中可(ke)以控制電(dian)(dian)(dian)流的強弱。

電容器在電路中有什么作用呢？

用(yong)(yong)電(dian)(dian)(dian)(dian)容器(qi)代替(ti)開(kai)關。接(jie)通(tong)電(dian)(dian)(dian)(dian)路(lu)時(shi)，我們看到小燈(deng)泡閃亮一下后(hou)就不再(zai)亮了(le)(le)。這是因為(wei)電(dian)(dian)(dian)(dian)容器(qi)在充電(dian)(dian)(dian)(dian)的(de)(de)瞬間(jian)，電(dian)(dian)(dian)(dian)路(lu)中(zhong)有(you)電(dian)(dian)(dian)(dian)流(liu)(liu)。而(er)充電(dian)(dian)(dian)(dian)過(guo)程(cheng)很快結束了(le)(le)，電(dian)(dian)(dian)(dian)容器(qi)充滿電(dian)(dian)(dian)(dian)荷后(hou)，電(dian)(dian)(dian)(dian)流(liu)(liu)消失了(le)(le)。電(dian)(dian)(dian)(dian)容器(qi)容量越小，充電(dian)(dian)(dian)(dian)所用(yong)(yong)時(shi)間(jian)越短暫，可見直流(liu)(liu)電(dian)(dian)(dian)(dian)是不能通(tong)過(guo)電(dian)(dian)(dian)(dian)容器(qi)的(de)(de)。若將(jiang)(jiang)電(dian)(dian)(dian)(dian)源(yuan)改為(wei)交(jiao)(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)源(yuan)，小燈(deng)泡將(jiang)(jiang)持續(xu)發光(guang)，若交(jiao)(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)頻(pin)率可以變化，那么(me)在相同的(de)(de)電(dian)(dian)(dian)(dian)壓下，高頻(pin)率交(jiao)(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)較(jiao)低(di)頻(pin)率交(jiao)(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)更易于通(tong)過(guo)同一個電(dian)(dian)(dian)(dian)容器(qi)而(er)使小燈(deng)泡更亮些。這些實(shi)驗可以說明電(dian)(dian)(dian)(dian)容器(qi)在電(dian)(dian)(dian)(dian)路(lu)中(zhong)，可以起“隔直流(liu)(liu)，通(tong)交(jiao)(jiao)(jiao)流(liu)(liu)”，“通(tong)高頻(pin)、阻低(di)頻(pin)”的(de)(de)作用(yong)(yong)。

晶體二極管在電路中(zhong)有什么作用呢？

我(wo)們將晶體二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)接在電(dian)路(lu)中(zhong)的開關位置上，燈泡發光(guang)，說明這(zhe)(zhe)時(shi)二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)導通(tong)，二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)的電(dian)阻(zu)（稱為正(zheng)向電(dian)阻(zu)）很(hen)小(xiao)。若將二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)兩極(ji)(ji)(ji)(ji)引(yin)腳對調，這(zhe)(zhe)時(shi)小(xiao)燈泡不亮了。這(zhe)(zhe)時(shi)二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)的電(dian)阻(zu)（稱為反向電(dian)阻(zu)）很(hen)大，電(dian)路(lu)中(zhong)幾(ji)乎(hu)沒有電(dian)流(liu)。這(zhe)(zhe)個(ge)現象(xiang)說明二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)有單向導電(dian)的特性。利(li)用二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)的這(zhe)(zhe)個(ge)特性，可(ke)使(shi)用二(er)(er)極(ji)(ji)(ji)(ji)管(guan)(guan)進行檢(jian)波和整流(liu)。