A piston-cylinder device contains 12 kg of saturated R-134a vapor at 3.2 bar. An electric source supplies 8 A current to a resistor within the cylinder for 4 minutes and there is heat transfer of 400 kJ to the system. During these energy interactions, the pressure is maintained constant in the cylinder. The refrigerant reaches a final temperature of 700C. Determine
a) The voltage of the source.
b) Show the expansion process for the R-134a on a P-v diagram. Label states, show property values, and indicate appropriate lines of constant pressure.