①電場：
每當兩個電(dian)極上(shang)存在著勢(shi)差（或電(dian)壓）時，在兩電(dian)極間的(de)煤質(zhi)中(zhong)(zhong)產(chan)生電(dian)廠(chang)，電(dian)廠(chang)中(zhong)(zhong)所存在絕(jue)緣媒質(zhi)叫(jiao)做介質(zhi)。各種(zhong)物質(zhi)有(you)不(bu)同(tong)介質(zhi)性(xing)質(zhi)，因(yin)(yin)此，電(dian)廠(chang)在不(bu)同(tong)媒質(zhi)中(zhong)(zhong)也有(you)不(bu)同(tong)的(de)特性(xing)。在這些電(dian)廠(chang)性(xing)質(zhi)當中(zhong)(zhong)，有(you)兩種(zhong)在介質(zhi)電(dian)熱上(shang)很重要，即介電(dian)系數(shu)和功率因(yin)(yin)數(shu)。這兩種(zhong)性(xing)質(zhi)的(de)量(liang)必須確定，以便對特種(zhong)介質(zhi)材料(liao)進(jin)行計算。

②電容：
兩(liang)電(dian)(dian)(dian)極(ji)(ji)(ji)間(jian)存在勢(shi)差時，則兩(liang)級板(ban)上帶有數量相(xiang)等而符號相(xiang)反的(de)電(dian)(dian)(dian)荷，一(yi)個在電(dian)(dian)(dian)極(ji)(ji)(ji)上的(de)電(dian)(dian)(dian)荷與(yu)兩(liang)極(ji)(ji)(ji)間(jian)勢(shi)差的(de)比數，即為電(dian)(dian)(dian)容量。電(dian)(dian)(dian)容對于分析(xi)電(dian)(dian)(dian)場里物質的(de)電(dian)(dian)(dian)路是很重要的(de)。簡單幾(ji)何體的(de)電(dian)(dian)(dian)極(ji)(ji)(ji)間(jian)的(de)電(dian)(dian)(dian)容很容易計(ji)算，例如兩(liang)個平行扁擔電(dian)(dian)(dian)極(ji)(ji)(ji)間(jian)（這兩(liang)個板(ban)極(ji)(ji)(ji)的(de)尺寸遠大于他(ta)們之間(jian)的(de)空隙(xi)）的(de)電(dian)(dian)(dian)容，可用(yong)方(fang)程式(shi)計(ji)算。