diàn wǎng / zhōng de / jiāo biàn diàn liú / huì / suí zhe / shí jiān / zhōu qī xìng de / gǎi biàn / fāng xiàng

电网中的交变电流会随着时间周期性地改变方向。

Alternating current in the power grid periodically changes direction over time.