E=Q2/τ e= 120/30
e=4 (eficiência da máquina frigorífica)

Exercício para entregar: Numa máquina frigorífica são retirados 240 J do congelador( fonte fria). No processo, a atmosfera ( fonte quente) recebe 300 J. Calcule o trabalho do compressor e a eficiência dessa máquina térmica.

Beryl states that insulation with the smallest possible thermal conductivity is best to keep a house warm in winter, but worst for keeping a house cool in summer. sapphire insists the reverse is true: low thermal conductivity is good in the summer, but bad in the winter. which one, if either is correct? a. beryl, because low thermal conductivity results in low heat transfer. b. beryl, because low thermal conductivity results in high heat transfer. d. sapphire, because low thermal conductivity results in high heat transfer. e. neither, because low heat transfer is desirable both in summer and in winter.