電(dian)阻器在電(dian)路中起什么作用(yong)呢?
將(jiang)電(dian)(dian)(dian)(dian)路中的開關(guan)換為1個(ge)470歐(ou)姆的電(dian)(dian)(dian)(dian)位器。旋轉電(dian)(dian)(dian)(dian)位器的轉柄,小(xiao)燈泡(pao)的亮度要(yao)隨著(zhu)電(dian)(dian)(dian)(dian)阻值的大小(xiao)而改(gai)變。電(dian)(dian)(dian)(dian)阻值越(yue)大,小(xiao)燈泡(pao)越(yue)暗。這說明電(dian)(dian)(dian)(dian)阻器在(zai)電(dian)(dian)(dian)(dian)路中可以控(kong)制電(dian)(dian)(dian)(dian)流(liu)的強(qiang)弱(ruo)。
電容(rong)器在電路中(zhong)有什么(me)作(zuo)用(yong)呢?
用電(dian)(dian)容器代(dai)替開關。接通(tong)電(dian)(dian)路時,我(wo)們看到小燈(deng)(deng)泡閃亮(liang)一下(xia)后(hou)(hou)就不再亮(liang)了。這是因為電(dian)(dian)容器在(zai)充(chong)(chong)電(dian)(dian)的(de)瞬間,電(dian)(dian)路中有電(dian)(dian)流(liu)。而(er)充(chong)(chong)電(dian)(dian)過(guo)(guo)程很快結束了,電(dian)(dian)容器充(chong)(chong)滿電(dian)(dian)荷(he)后(hou)(hou),電(dian)(dian)流(liu)消失(shi)了。電(dian)(dian)容器容量越小,充(chong)(chong)電(dian)(dian)所用時間越短暫,可見直流(liu)電(dian)(dian)是不能通(tong)過(guo)(guo)電(dian)(dian)容器的(de)。若將電(dian)(dian)源(yuan)改為交流(liu)電(dian)(dian)源(yuan),小燈(deng)(deng)泡將持(chi)續發光(guang),若交流(liu)電(dian)(dian)頻(pin)(pin)率可以(yi)變化(hua),那么在(zai)相同的(de)電(dian)(dian)壓(ya)下(xia),高頻(pin)(pin)率交流(liu)電(dian)(dian)較低頻(pin)(pin)率交流(liu)電(dian)(dian)更易于通(tong)過(guo)(guo)同一個電(dian)(dian)容器而(er)使小燈(deng)(deng)泡更亮(liang)些。這些實驗可以(yi)說明電(dian)(dian)容器在(zai)電(dian)(dian)路中,可以(yi)起“隔(ge)直流(liu),通(tong)交流(liu)”,“通(tong)高頻(pin)(pin)、阻低頻(pin)(pin)”的(de)作(zuo)用。
晶(jing)體二極(ji)管在(zai)電(dian)路中(zhong)有什么作用呢?
我們將晶體二(er)極(ji)(ji)管接(jie)在(zai)電路(lu)(lu)中的(de)開關(guan)位(wei)置上,燈(deng)泡發光,說明(ming)這(zhe)(zhe)時二(er)極(ji)(ji)管導通(tong),二(er)極(ji)(ji)管的(de)電阻(zu)(稱為正向(xiang)電阻(zu))很小(xiao)。若(ruo)將二(er)極(ji)(ji)管兩(liang)極(ji)(ji)引腳對調,這(zhe)(zhe)時小(xiao)燈(deng)泡不亮了。這(zhe)(zhe)時二(er)極(ji)(ji)管的(de)電阻(zu)(稱為反向(xiang)電阻(zu))很大(da),電路(lu)(lu)中幾乎沒有電流(liu)。這(zhe)(zhe)個現象說明(ming)二(er)極(ji)(ji)管有單向(xiang)導電的(de)特(te)性。利用(yong)二(er)極(ji)(ji)管的(de)這(zhe)(zhe)個特(te)性,可使用(yong)二(er)極(ji)(ji)管進行檢波和整流(liu)。