電(dian)(dian)阻器是(shi)限制電(dian)(dian)流的元(yuan)件(jian)，通(tong)常簡(jian)稱(cheng)為電(dian)(dian)阻，是(shi)一種最常用的電(dian)(dian)子元(yuan)件(jian)，普(pu)遍應用在各類(lei)電(dian)(dian)子電(dian)(dian)路中。不但金屬(shu)導體有(you)(you)電(dian)(dian)阻，其他(ta)物(wu)體也有(you)(you)電(dian)(dian)阻。

簡單來說，電(dian)(dian)阻就(jiu)是(shi)指電(dian)(dian)流在(zai)電(dian)(dian)路(lu)中(zhong)所遇到的阻力(li)，或者說是(shi)指物(wu)體對(dui)電(dian)(dian)流的阻礙才能。電(dian)(dian)阻越(yue)大，電(dian)(dian)流所遭(zao)到的阻力(li)就(jiu)越(yue)大，因而(er)電(dian)(dian)流就(jiu)越(yue)小。反之，電(dian)(dian)阻越(yue)小，電(dian)(dian)流所遭(zao)到的阻力(li)就(jiu)越(yue)小，因而(er)電(dian)(dian)流就(jiu)越(yue)大。

電阻(zu)的(de)(de)符號(hao)是“R”。電阻(zu)的(de)(de)單(dan)位(wei)(wei)為歐(ou)姆，簡稱歐(ou)，用(yong)字母(mu)“Ω”表示(shi)。常用(yong)的(de)(de)電阻(zu)單(dan)位(wei)(wei)還(huan)有千(qian)歐(ou)姆（KΩ），兆歐(ou)姆（MΩ）。