Thanks for your clarification. To be honest I studied the article grammar today and faced with both of them and I couldn't make the difference between them out. In all I have problem in using article, I don't know how I can deal with this issues. I have studied a lot but I forgot and can't thoroughly.

99.5% of the time you’ll want to use “watch TV.” To watch TV is to view television programs: “After work I usually watch TV for an hour or two.” I suppose there are extremely rare circumstances in which “watch the TV” would be appropriate, but in that sense, it would mean “watch over” — “Watch the TV when I’m gone to make sure that nobody steals it.”

To watch TV

I like to watch TV (general) I'm going to watch the TV for a while (specifically, THE television in this room) If in doubt, watch TV works in all situations :)