電阻器在電路中起什么作用呢？

將(jiang)電(dian)路中(zhong)的(de)開關換為1個470歐姆(mu)的(de)電(dian)位器(qi)。旋轉電(dian)位器(qi)的(de)轉柄，小燈(deng)(deng)泡的(de)亮度要隨著電(dian)阻值的(de)大小而改變。電(dian)阻值越大，小燈(deng)(deng)泡越暗(an)。這說明電(dian)阻器(qi)在電(dian)路中(zhong)可以控制電(dian)流的(de)強弱。

電容器在電路中(zhong)有什(shen)么(me)作用呢？

用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)代替開關。接通(tong)電(dian)(dian)(dian)(dian)(dian)(dian)路時，我們(men)看(kan)到小燈泡閃(shan)亮(liang)一下后(hou)就不(bu)再亮(liang)了。這是因為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)在(zai)充電(dian)(dian)(dian)(dian)(dian)(dian)的(de)瞬間，電(dian)(dian)(dian)(dian)(dian)(dian)路中(zhong)有電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)。而充電(dian)(dian)(dian)(dian)(dian)(dian)過程很快結(jie)束了，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)充滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)荷后(hou)，電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)消失了。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)容(rong)(rong)量越(yue)小，充電(dian)(dian)(dian)(dian)(dian)(dian)所用(yong)時間越(yue)短暫，可見直流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)是不(bu)能通(tong)過電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)的(de)。若將(jiang)電(dian)(dian)(dian)(dian)(dian)(dian)源改為(wei)交(jiao)(jiao)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)源，小燈泡將(jiang)持續發光(guang)，若交(jiao)(jiao)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)頻率可以(yi)變化，那么在(zai)相同的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓下，高頻率交(jiao)(jiao)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)較低頻率交(jiao)(jiao)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)更易于(yu)通(tong)過同一個電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)而使小燈泡更亮(liang)些(xie)。這些(xie)實驗可以(yi)說明(ming)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)路中(zhong)，可以(yi)起“隔直流(liu)(liu)(liu)(liu)，通(tong)交(jiao)(jiao)流(liu)(liu)(liu)(liu)”，“通(tong)高頻、阻低頻”的(de)作用(yong)。

晶體二極管(guan)在電路中有什么(me)作(zuo)用呢？

我們將(jiang)晶體二(er)極(ji)(ji)管接在電(dian)路中的(de)(de)開(kai)關位置上，燈泡發光，說明這時二(er)極(ji)(ji)管導通，二(er)極(ji)(ji)管的(de)(de)電(dian)阻（稱(cheng)為(wei)正(zheng)向電(dian)阻）很(hen)(hen)小。若將(jiang)二(er)極(ji)(ji)管兩極(ji)(ji)引腳(jiao)對(dui)調，這時小燈泡不亮了。這時二(er)極(ji)(ji)管的(de)(de)電(dian)阻（稱(cheng)為(wei)反向電(dian)阻）很(hen)(hen)大(da)，電(dian)路中幾乎沒有電(dian)流。這個(ge)現象說明二(er)極(ji)(ji)管有單向導電(dian)的(de)(de)特性(xing)。利(li)用二(er)極(ji)(ji)管的(de)(de)這個(ge)特性(xing)，可使(shi)用二(er)極(ji)(ji)管進行檢波和(he)整流。