在我看來，“了”在句子中位置的差別是會造成句子含義有所差別。但是在一般情況下，具體差別還是要聯繫上下文才能夠被分辨出來。 從《現代漢語大詞典》中可以找到詳細的解釋。 “了”：助詞。 1.用在形容詞或動詞後面，表示已經發生動作或變化。 a）用於實際已經發生的動作或變化。 “我做了飯”，此處強調的點在於主語“我”和“做了”這個已經完成的動作，突出不是別的人做了飯。 又例：這個小組受到了表揚。 2.用在句子末尾或句中停頓的地方，表示變化或出現新的情況。 a）表示已經出現或將要出現某種情況。 “我做飯了”，其語氣顯然沒有上一句那麼強烈。表示我在過去某個時段“我”有過這樣一個動作，僅此而已。 又例：剛才下過雨了。

(1) 我做了飯 ——An act (2) 我做飯了 ——A state

The first focuses on the action itself which is done, and the second on the fact that it is finished.

我做了饭=i have done sth 我做饭了=i am going to do sth

I would like to put them into a certain suitaiton, the first one sounds like" I cooked the meal" ( with the note of "I made it or I did that") What have you done today? I COOKED the meal! The latter one actually is a statement with very light note. Personally, theres's slight difference betweent them.