은주리님께서 과거형은 잘 퍼담아놓으셨는데 복수형은 초등게시판 14314번에 가시면 상당히 자세하게 설명되어 있습니다. 초등게시판에 먼저 가셔서 확인하고 은주리님의 답글을 읽으면 이해가 잘되실듯싶네요.

저도 방금 배우고 왔습니다.

사이트에 있는거 퍼와 보았습니다.

 after an unvoiced consonant sound (sh/ s / ch / p / k / f ) we pronounce /t/: wash (/sh/) - washed (/t/); kiss (/s/) - kissed (/t/); work (/k/) - worked (/t/); hope (/p/) - hoped (/t/); laugh (/f/) - laughed (/t/)
 after a vowel and voiced consonant sounds we pronounce /d/: phone (/n/) - phoned (/d/); judge (/dg/) - judged (/d/); turn (/n/) - turned (/d/); play (/ei/) - played (/d/); follow (/ou/) - followed (/d/)
 after /t/ and /d/ sounds we pronounce /-id/: visite (/t/) - visited (/id/); start (/t/) - started (/id/); need (/d/) - needed (/id/)