電阻器在電路中起什么(me)作用呢？

將(jiang)電路中的(de)開關換為1個(ge)470歐姆的(de)電位(wei)(wei)器(qi)。旋轉電位(wei)(wei)器(qi)的(de)轉柄，小燈泡(pao)的(de)亮(liang)度要(yao)隨著電阻(zu)值(zhi)的(de)大小而改(gai)變。電阻(zu)值(zhi)越(yue)大，小燈泡(pao)越(yue)暗(an)。這說明電阻(zu)器(qi)在電路中可以控(kong)制電流的(de)強弱。

電(dian)容(rong)器(qi)在(zai)電(dian)路中有什么作用呢(ni)？

用電(dian)(dian)(dian)(dian)容(rong)(rong)器代替開(kai)關。接通電(dian)(dian)(dian)(dian)路(lu)(lu)時，我們看到(dao)小(xiao)燈泡(pao)閃亮(liang)(liang)一(yi)下后就不(bu)(bu)再亮(liang)(liang)了(le)。這(zhe)是因為(wei)電(dian)(dian)(dian)(dian)容(rong)(rong)器在(zai)充(chong)電(dian)(dian)(dian)(dian)的(de)瞬間(jian)，電(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)有電(dian)(dian)(dian)(dian)流(liu)。而充(chong)電(dian)(dian)(dian)(dian)過(guo)程很(hen)快結(jie)束了(le)，電(dian)(dian)(dian)(dian)容(rong)(rong)器充(chong)滿(man)電(dian)(dian)(dian)(dian)荷后，電(dian)(dian)(dian)(dian)流(liu)消失(shi)了(le)。電(dian)(dian)(dian)(dian)容(rong)(rong)器容(rong)(rong)量(liang)越小(xiao)，充(chong)電(dian)(dian)(dian)(dian)所用時間(jian)越短(duan)暫，可見直流(liu)電(dian)(dian)(dian)(dian)是不(bu)(bu)能(neng)通過(guo)電(dian)(dian)(dian)(dian)容(rong)(rong)器的(de)。若將(jiang)電(dian)(dian)(dian)(dian)源改為(wei)交(jiao)流(liu)電(dian)(dian)(dian)(dian)源，小(xiao)燈泡(pao)將(jiang)持續(xu)發光，若交(jiao)流(liu)電(dian)(dian)(dian)(dian)頻(pin)率(lv)(lv)可以(yi)(yi)變化，那么在(zai)相同(tong)的(de)電(dian)(dian)(dian)(dian)壓下，高頻(pin)率(lv)(lv)交(jiao)流(liu)電(dian)(dian)(dian)(dian)較低頻(pin)率(lv)(lv)交(jiao)流(liu)電(dian)(dian)(dian)(dian)更(geng)易(yi)于通過(guo)同(tong)一(yi)個電(dian)(dian)(dian)(dian)容(rong)(rong)器而使小(xiao)燈泡(pao)更(geng)亮(liang)(liang)些。這(zhe)些實(shi)驗可以(yi)(yi)說明電(dian)(dian)(dian)(dian)容(rong)(rong)器在(zai)電(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)，可以(yi)(yi)起“隔直流(liu)，通交(jiao)流(liu)”，“通高頻(pin)、阻(zu)低頻(pin)”的(de)作用。

晶體二(er)極管在電路中有什么(me)作用呢？

我們將(jiang)晶體二極(ji)管(guan)(guan)(guan)(guan)(guan)接在電(dian)路中的(de)開關(guan)位置上，燈泡發光，說明這時(shi)(shi)二極(ji)管(guan)(guan)(guan)(guan)(guan)導通(tong)，二極(ji)管(guan)(guan)(guan)(guan)(guan)的(de)電(dian)阻（稱為(wei)正向電(dian)阻）很小(xiao)。若(ruo)將(jiang)二極(ji)管(guan)(guan)(guan)(guan)(guan)兩極(ji)引腳對(dui)調，這時(shi)(shi)小(xiao)燈泡不亮了。這時(shi)(shi)二極(ji)管(guan)(guan)(guan)(guan)(guan)的(de)電(dian)阻（稱為(wei)反向電(dian)阻）很大，電(dian)路中幾乎沒有電(dian)流(liu)。這個現象說明二極(ji)管(guan)(guan)(guan)(guan)(guan)有單(dan)向導電(dian)的(de)特(te)性。利用二極(ji)管(guan)(guan)(guan)(guan)(guan)的(de)這個特(te)性，可使用二極(ji)管(guan)(guan)(guan)(guan)(guan)進行檢(jian)波(bo)和整流(liu)。