1、達(da)到(dao)控制(zhi)變量(liang)的目的

　　欲探(tan)究(jiu)電(dian)(dian)(dian)流(liu)與電(dian)(dian)(dian)阻及電(dian)(dian)(dian)壓(ya)的關系，要采用控(kong)制變量(liang)法進(jin)行(xing)實驗。在探(tan)究(jiu)電(dian)(dian)(dian)流(liu)與電(dian)(dian)(dian)阻的關系時，應(ying)該控(kong)制電(dian)(dian)(dian)壓(ya)不變。

　　2、達到保護電路的(de)目的(de)

　　根(gen)據歐姆定(ding)律I=U/R知道，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓一定(ding)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)總(zong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)越(yue)(yue)小，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流就越(yue)(yue)大(da)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)的(de)(de)某些元件如電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流表(biao)就越(yue)(yue)有損壞的(de)(de)可能。因此(ci)，在伏(fu)安法測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)、用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流表(biao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓表(biao)測小燈(deng)泡的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)功(gong)率(lv)等多(duo)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)學實(shi)驗中(zhong)，都配有雙管滑(hua)線滑(hua)動變(bian)阻(zu)器(qi)(qi)。教材反(fan)復強(qiang)調，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)連接完畢(bi)閉合開(kai)關前，一定(ding)要將雙管滑(hua)線滑(hua)動變(bian)阻(zu)器(qi)(qi)在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)的(de)(de)阻(zu)值調至。目的(de)(de)是(shi)為了盡可能增大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)總(zong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流達到小，從而達到保護電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)目的(de)(de)。如伏(fu)安法測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)、用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流表(biao)和(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓表(biao)測小燈(deng)泡的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)功(gong)率(lv)等實(shi)驗都利用了雙管滑(hua)線滑(hua)動變(bian)阻(zu)器(qi)(qi)保護電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)作用。

　　3、達到改變電壓的(de)目的(de)

　　4、達(da)到改(gai)變小燈泡(pao)的(de)(de)亮度(du)的(de)(de)目的(de)(de)?實驗(yan)要求用伏安法測(ce)出燈泡(pao)亮度(du)由不(bu)亮到燈絲暗紅、微弱發(fa)光及至正常發(fa)光時(shi)的(de)(de)電流與電壓。這里整(zheng)個過(guo)程的(de)(de)多次測(ce)量都依賴于調節(jie)電路(lu)中(zhong)的(de)(de)雙管滑(hua)線(xian)滑(hua)動(dong)變阻器(qi)。通過(guo)改(gai)變雙管滑(hua)線(xian)滑(hua)動(dong)變阻器(qi)在電路(lu)中(zhong)的(de)(de)電阻，使(shi)小燈泡(pao)的(de)(de)電流和電壓相應(ying)發(fa)生改(gai)變，從而實際功(gong)率(lv)逐步(bu)增加，亮度(du)逐漸變亮。

　　5、達到(dao)實(shi)現調整電壓(ya)到(dao)值的目的

　　根據功(gong)率的(de)(de)(de)公式P=UI知道，小(xiao)(xiao)(xiao)燈泡(pao)(pao)的(de)(de)(de)額定功(gong)率應(ying)該等(deng)于小(xiao)(xiao)(xiao)燈泡(pao)(pao)的(de)(de)(de)額定電(dian)(dian)壓(ya)與額定電(dian)(dian)流的(de)(de)(de)乘積。因此，用實驗測(ce)小(xiao)(xiao)(xiao)燈泡(pao)(pao)的(de)(de)(de)額定功(gong)率時，必(bi)須要將小(xiao)(xiao)(xiao)燈泡(pao)(pao)兩端的(de)(de)(de)實際電(dian)(dian)壓(ya)調整到與額定電(dian)(dian)壓(ya)的(de)(de)(de)大(da)小(xiao)(xiao)(xiao)相等(deng)。這(zhe)里仍然(ran)是利用滑(hua)雙管(guan)滑(hua)線滑(hua)動變(bian)阻(zu)器通過改變(bian)其(qi)在電(dian)(dian)路(lu)中的(de)(de)(de)阻(zu)值來達到調整電(dian)(dian)壓(ya)到值的(de)(de)(de)目(mu)的(de)(de)(de)。此處容易與控制變(bian)量這(zhe)一目(mu)的(de)(de)(de)相混淆。

　　6、達(da)到改變電流大小的目的

　　當探(tan)究電(dian)(dian)(dian)(dian)磁(ci)(ci)鐵(tie)磁(ci)(ci)性強弱與電(dian)(dian)(dian)(dian)流(liu)大小的(de)(de)關(guan)系時，應當控制電(dian)(dian)(dian)(dian)磁(ci)(ci)鐵(tie)線(xian)圈的(de)(de)匝數不(bu)變(bian)，而改(gai)變(bian)線(xian)圈中(zhong)電(dian)(dian)(dian)(dian)流(liu)的(de)(de)大小。在實驗時，將線(xian)圈與滑(hua)動(dong)變(bian)阻串聯(lian)，就可以達到通過改(gai)變(bian)變(bian)阻器在電(dian)(dian)(dian)(dian)路中(zhong)的(de)(de)阻值而改(gai)變(bian)線(xian)圈中(zhong)電(dian)(dian)(dian)(dian)流(liu)的(de)(de)目的(de)(de)。當然(ran)，由于線(xian)圈的(de)(de)電(dian)(dian)(dian)(dian)阻比較小，該變(bian)阻器仍然(ran)要承擔保護電(dian)(dian)(dian)(dian)路的(de)(de)責(ze)任。

　　7、達到實現多次測量的目的

　　在(zai)用伏安法測(ce)量電阻實驗中(zhong)，用雙管滑線滑動變阻器來實現(xian)多(duo)次測(ce)量，以(yi)達到多(duo)次測(ce)量求平均(jun)值而減小誤差的目的。