当你为你的吐司炉——或者电视、吸尘器——插好插头、打开电源时，电能便以交流电的形式为这些家用电器供电。
PLUG in your toaster—or your television or your vacuum cleaner—and the electricity that surges through it is an alternating current.
在家里，许多家用电器在拔下插头的前几分钟里都会发出足够多余热。
At home, many household items give off enough residual heat to pull the plug a few minutes early.
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