Reff = 12/8 + 1 = 5/2
i = 6/(5/2) = 12/5Amp.
2000J of heat raises the temp. by 1K
5832J of heat raises the temp. by 2.916K.
(b) When 6Ω resistor get burnt Reff = 1 + 2 = 3Ω
i = 6/3 = 2Amp.
Heat = 2 × 2 × 2 ×15 × 60 = 7200J
2000J raises the temp. by 1K
7200J raises the temp by 3.6k