電阻器在電路中起什么作用呢？

將電(dian)路中的(de)開(kai)關換為1個470歐(ou)姆的(de)電(dian)位器(qi)。旋轉電(dian)位器(qi)的(de)轉柄，小燈泡的(de)亮度要隨著電(dian)阻值的(de)大小而(er)改變。電(dian)阻值越大，小燈泡越暗。這說明電(dian)阻器(qi)在(zai)電(dian)路中可以控制電(dian)流(liu)的(de)強弱。

電容器在電路(lu)中有什(shen)么作(zuo)用呢？

用電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)代替開關。接通(tong)(tong)電(dian)(dian)(dian)(dian)路時，我們看到(dao)小燈泡(pao)閃亮一下后(hou)就不再亮了(le)(le)。這(zhe)是因(yin)為(wei)(wei)電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)在充(chong)(chong)電(dian)(dian)(dian)(dian)的(de)瞬間，電(dian)(dian)(dian)(dian)路中(zhong)有(you)電(dian)(dian)(dian)(dian)流(liu)。而充(chong)(chong)電(dian)(dian)(dian)(dian)過(guo)程很快結(jie)束了(le)(le)，電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)充(chong)(chong)滿電(dian)(dian)(dian)(dian)荷后(hou)，電(dian)(dian)(dian)(dian)流(liu)消失了(le)(le)。電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)容(rong)量越小，充(chong)(chong)電(dian)(dian)(dian)(dian)所(suo)用時間越短(duan)暫，可見(jian)直流(liu)電(dian)(dian)(dian)(dian)是不能(neng)通(tong)(tong)過(guo)電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)的(de)。若將(jiang)電(dian)(dian)(dian)(dian)源(yuan)改(gai)為(wei)(wei)交流(liu)電(dian)(dian)(dian)(dian)源(yuan)，小燈泡(pao)將(jiang)持續發光(guang)，若交流(liu)電(dian)(dian)(dian)(dian)頻率(lv)(lv)可以(yi)變化(hua)，那么在相同(tong)的(de)電(dian)(dian)(dian)(dian)壓下，高(gao)頻率(lv)(lv)交流(liu)電(dian)(dian)(dian)(dian)較(jiao)低(di)(di)頻率(lv)(lv)交流(liu)電(dian)(dian)(dian)(dian)更易于通(tong)(tong)過(guo)同(tong)一個(ge)電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)而使(shi)小燈泡(pao)更亮些。這(zhe)些實驗可以(yi)說明電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)在電(dian)(dian)(dian)(dian)路中(zhong)，可以(yi)起“隔直流(liu)，通(tong)(tong)交流(liu)”，“通(tong)(tong)高(gao)頻、阻低(di)(di)頻”的(de)作用。

晶體二極(ji)管(guan)在電路(lu)中有什(shen)么作(zuo)用呢(ni)？

我們(men)將晶體二(er)極(ji)(ji)(ji)管(guan)(guan)接在(zai)電(dian)路(lu)中的(de)(de)(de)開關位置上，燈泡發光，說明(ming)這時二(er)極(ji)(ji)(ji)管(guan)(guan)導(dao)(dao)通，二(er)極(ji)(ji)(ji)管(guan)(guan)的(de)(de)(de)電(dian)阻(zu)（稱為(wei)正向(xiang)電(dian)阻(zu)）很小(xiao)。若將二(er)極(ji)(ji)(ji)管(guan)(guan)兩極(ji)(ji)(ji)引腳對調，這時小(xiao)燈泡不(bu)亮(liang)了。這時二(er)極(ji)(ji)(ji)管(guan)(guan)的(de)(de)(de)電(dian)阻(zu)（稱為(wei)反向(xiang)電(dian)阻(zu)）很大(da)，電(dian)路(lu)中幾乎(hu)沒有電(dian)流(liu)。這個現象說明(ming)二(er)極(ji)(ji)(ji)管(guan)(guan)有單向(xiang)導(dao)(dao)電(dian)的(de)(de)(de)特性(xing)。利用二(er)極(ji)(ji)(ji)管(guan)(guan)的(de)(de)(de)這個特性(xing)，可(ke)使用二(er)極(ji)(ji)(ji)管(guan)(guan)進行檢波和整流(liu)。