電阻(zu)器在電路中起什么作用(yong)呢？

將電(dian)(dian)路(lu)中的開關換(huan)為1個470歐姆(mu)的電(dian)(dian)位(wei)器。旋(xuan)轉電(dian)(dian)位(wei)器的轉柄，小燈泡(pao)的亮度要隨(sui)著(zhu)電(dian)(dian)阻值的大(da)小而改變(bian)。電(dian)(dian)阻值越大(da)，小燈泡(pao)越暗(an)。這說(shuo)明電(dian)(dian)阻器在電(dian)(dian)路(lu)中可以控(kong)制(zhi)電(dian)(dian)流(liu)的強弱(ruo)。

電容(rong)器在電路中(zhong)有什么作(zuo)用(yong)呢？

用電(dian)(dian)容(rong)器代替開(kai)關。接通電(dian)(dian)路時，我們看到小(xiao)燈(deng)泡(pao)(pao)閃(shan)亮(liang)一(yi)下(xia)后(hou)就不(bu)再亮(liang)了(le)。這(zhe)是因為電(dian)(dian)容(rong)器在(zai)(zai)充(chong)(chong)電(dian)(dian)的(de)(de)(de)瞬間，電(dian)(dian)路中有電(dian)(dian)流(liu)(liu)(liu)。而(er)充(chong)(chong)電(dian)(dian)過(guo)程很快結(jie)束了(le)，電(dian)(dian)容(rong)器充(chong)(chong)滿(man)電(dian)(dian)荷后(hou)，電(dian)(dian)流(liu)(liu)(liu)消失了(le)。電(dian)(dian)容(rong)器容(rong)量越小(xiao)，充(chong)(chong)電(dian)(dian)所用時間越短暫(zan)，可見直(zhi)流(liu)(liu)(liu)電(dian)(dian)是不(bu)能通過(guo)電(dian)(dian)容(rong)器的(de)(de)(de)。若(ruo)將電(dian)(dian)源改(gai)為交(jiao)(jiao)流(liu)(liu)(liu)電(dian)(dian)源，小(xiao)燈(deng)泡(pao)(pao)將持續發光，若(ruo)交(jiao)(jiao)流(liu)(liu)(liu)電(dian)(dian)頻(pin)(pin)率(lv)可以變化，那么在(zai)(zai)相同(tong)的(de)(de)(de)電(dian)(dian)壓下(xia)，高頻(pin)(pin)率(lv)交(jiao)(jiao)流(liu)(liu)(liu)電(dian)(dian)較低頻(pin)(pin)率(lv)交(jiao)(jiao)流(liu)(liu)(liu)電(dian)(dian)更(geng)(geng)易于(yu)通過(guo)同(tong)一(yi)個(ge)電(dian)(dian)容(rong)器而(er)使小(xiao)燈(deng)泡(pao)(pao)更(geng)(geng)亮(liang)些。這(zhe)些實驗可以說明電(dian)(dian)容(rong)器在(zai)(zai)電(dian)(dian)路中，可以起“隔直(zhi)流(liu)(liu)(liu)，通交(jiao)(jiao)流(liu)(liu)(liu)”，“通高頻(pin)(pin)、阻低頻(pin)(pin)”的(de)(de)(de)作用。

晶(jing)體二極管在電路中有什(shen)么作用(yong)呢？

我(wo)們將晶(jing)體二(er)極(ji)管(guan)(guan)接在電(dian)(dian)路(lu)中的(de)開(kai)關位置(zhi)上，燈泡發光，說明這(zhe)時(shi)二(er)極(ji)管(guan)(guan)導通，二(er)極(ji)管(guan)(guan)的(de)電(dian)(dian)阻(zu)（稱(cheng)為(wei)(wei)正向(xiang)電(dian)(dian)阻(zu)）很(hen)小(xiao)。若(ruo)將二(er)極(ji)管(guan)(guan)兩極(ji)引腳對調，這(zhe)時(shi)小(xiao)燈泡不(bu)亮了。這(zhe)時(shi)二(er)極(ji)管(guan)(guan)的(de)電(dian)(dian)阻(zu)（稱(cheng)為(wei)(wei)反向(xiang)電(dian)(dian)阻(zu)）很(hen)大，電(dian)(dian)路(lu)中幾乎沒有電(dian)(dian)流。這(zhe)個(ge)現象說明二(er)極(ji)管(guan)(guan)有單向(xiang)導電(dian)(dian)的(de)特(te)(te)性(xing)。利用二(er)極(ji)管(guan)(guan)的(de)這(zhe)個(ge)特(te)(te)性(xing)，可使用二(er)極(ji)管(guan)(guan)進行檢波(bo)和整(zheng)流。