ΔW=ΔU\Delta \mathrm{W}=\Delta \mathrm{U}ΔW=ΔU
ΔW=−ΔU\Delta \mathrm{W}=-\Delta \mathrm{U}ΔW=−ΔU
ΔQ=ΔU\Delta \mathrm{Q}=\Delta \mathrm{U}ΔQ=ΔU
ΔQ=−ΔU\Delta \mathrm{Q}=-\Delta \mathrm{U}ΔQ=−ΔU