The balloons became electrically-charged from rubbing and could stick to the wall.

electrically-charged 是由形容词 electric（电的）加上后缀 -al 变成 electrically（电气方面地），再与过去分词 charged（带电的）组合而成的复合形容词。electric 来自名词 electricity（电），charged 来自动词 charge（充电）。 electrically-charged 表示"带电的"，指物体通过摩擦等方式获得了静电荷。