R3: explain how a speaker works by explaining why each part is required. what role does the function generator play? what role does the magnet play? what role does the coil play? what role does the paper play?
pi3: summarize r3’s answer by explaining why the ta’s homemade earbud is so much superior to the one that you made.

Precipitation hardening can be achieved in many light alloys by a three-step heat treatment. what is carried out and what is the purpose at each step? why is such a treatment necessary based on the nucleation and growth theory of phase transformation. compare this treatment with tempering martensite for carbon steels (similarities and differences).