Tiān-chû-la̍t (electromagnetic force) sī tiān-chû-tiûⁿ tùi ū tiān-hō ê lia̍p-chú sán-seng ê 1 chióng la̍t. Che sī 4 chióng ki-pún-la̍t ê 1 chióng, lēng-goā 3 chióng sī kiông-la̍t, jio̍k-la̍t ham tāng-la̍t. Chit 4 chióng í-goā ê la̍t lóng sī ùi chiah-ê ki-pún-la̍t lâi--ê.

Lán seng-oa̍h--nih khoàⁿ ē tio̍h ê hiān-siōng tāi-thé lóng sī tiān-chû-la̍t ham tāng-la̍t ê chok-iōng. Kán-tan kóng, chhiūⁿ lán teh "sak" iah sī "giú" mi̍h-kiāⁿ, sī lán sin-thé ham mi̍h-kiāⁿ lāi-té-bīn ê hun-chú ham hun-chú teh chok-iōng; ah hun-chú tiong-ng ê chok-iōng iū-koh sī goân-chú ham goân-chú teh chok-iōng; ah goân-chú tiong-ng ê chok-iōng lóng sī tiān-chû-la̍t tùi ū tiān-hō ê iông-chú ham tiān-chú ê éng-hióng. Lēng-goā, só͘-ū ê hoà-ha̍k hiān-siōng lóng sī tī tiān-chú kúi-tō leh chok-iōng.