A rigid tank contains 2 kg of air at 200 kPa and ambient temperature, 20°C. An electric current now passes through a resistor inside the tank. After a total of 100 kJ of electrical work has crossed the boundary, the air temperature inside is 80°C. Is this possible?
C.V.: Air in tank out to ambient;
Assume constant specific heat then energy equation gives
1Q2 = mCv(T2 − T1) + 1W2 = 2 x 0.717(80 – 20) – 100 = −14.0 kJ Change in *
