Sign convention of heat and work

1. Heat (q)
  Case I:
 When heat is absorbed by the system, q = +ve.

  Case II:
 When heat is released by the system, q = -ve.

2. Work (w)
  Case I: (Work of Expansion)
 When work is done by the system, w = +ve.

  Case II: (Work of Compression)
 When work is done on the system, w = -ve.

Have a question? Ask us in our discussion forum.