看完电视后要及时关掉用英语怎么说

"Turn off the TV after watching" 可以用英文表达为 "Turn off the television after watching it."

其中, "turn off" 意为 "关掉"， "television" 意为 "电视"， "after" 意为 "在...之后"， "watching" 意为 "看"。

一些例句如下:

Remember to turn off the television after watching it.
Don't forget to turn off the TV after you're done watching.
Make sure to turn off the television after you finish watching.

这种表达方式来自于英语日常交流中对于电器的操作的描述，经常用于提醒或建议别人在使用完电器后关闭电源。