Can someone use my IP address for wifi hack torrents i.e hack into a secured wifi to download bit torrent?

Yes, it is possible for someone to use your IP for wifi hack torrents, even if you use WPA2.

• There are different ways how to do it:
  
• The faster is WPS Pixie Dust Attack (within some seconds),
  
• the next is Reaver (some hours, also need enabled WPS),
  
• and the slowest is the off-line Dictionary attack (days or weeks, or even never).
  
• All depends on your security settings on your router (Access Point) and the uniqueness of your password, and - of course - of the the possibilities and the level of your attacker.
  
• And, yes, then the attacker presents himself (for outer world) with the same IP address as you, assigned to you by your Internet Service Provider (as anybody in your family).