TT: mFe = 400g=0,4kg ; to1 = 70oC
mnc = 500g = 0,5kg ; to2 = 20oC
cnc = 4200 J/kg.K ; cFe = 460J/kg.K
=> to = ?
giai:
nhiet luong nc thu vao:
Qthu = mnc . cnc . (to - to2) = 2100to - 42000
nhiet luong Fe toa ra:
Qtoa =mFe . cFe .(to1 - to) = 12880 - 184to
theo PTCBN ta co: Qthu = Qtoa
\(\Leftrightarrow2100t^o-42000=12880-184t^o\)
\(\Leftrightarrow2284t^o=54880\Rightarrow t^o\approx24^oC\)