The  past simple tense and  past participle of all regular verbs end in -ed. For example:

work, worked , worked

In addition, many adjectives are made from the past participle and so end in -ed. For example:

I like painted furniture.

The question is, how do we pronounce the -ed? The answer is, in 3 ways:

  • /ɪd/
  • /t/
  • /d/
If the base verb ends in one of these soundsexample base verb*example with -edpronounce the -ed asextra syllable?
/t/wantwanted/ ɪd/yes
/d/endended
unvoiced/p/hopehoped/ t/no
/f/laughlaughed
/s/faxfaxed
/ʃ/washwashed
/ʧ/watchwatched
/k/likeliked
voicedall other sounds, egplayplayed/ d/
allowallowed
begbegged

*Note that it is the sound  that is important, not the letter or spelling. For example, fax  ends in the letter x  but the sound /s/; like  ends in the letter e  but the sound /k/.

Exceptions

The following -ed  words used as adjectives are pronounced with /ɪd/:

  • aged
  • dogged
  • ragged
  • blessed
  • learned
  • wicked
  • crooked
  • naked
  • wretched

So we say:

  • an aged man /ɪd/
  • a blessed nuisance /ɪd/
  • a dogged persistence /ɪd/
  • a learned professor - the professor, who was truly learned /ɪd/
  • a wretched beggar - the beggar was wretched /ɪd/

But when used as real verbs (past simple and past participle), the normal rules apply and we say:

  • he aged quickly /d/
  • he blessed me /t/
  • they dogged him /d/
  • he has learned well /d/ or /t/

sources : Original Link