Most torrents have multiple files in it. My question is that can i get magnet link of a one particular file in a torrent?
You may not be able to do that but with
utorrent you can choose to download only the desired files.
You can also do this even if all files were previously selected. Click on the torrent that you're downloading in the list then select Files tab, and then right click on the file that you don't want to download and then select not to download it as shown below: