Thermodynamics

• First law of thermodynamics

  Heat added to system = increase in internal temperature + work done by system
• Compression is work on the system, so work is -ve and internal energy increases
• Expansion is work by the system, so work is +ve and internal energy decreases
• Change in internal energy = - Work
• Isothermal is when temperature is constant
• Isothermal restriction?


  change in U = 0
• Isothermal first law?


  Q = W
• Constant volume restriction?


  W=0
• Constant V first law?

  Q = change in U
• Constant P restriction?


  W = p x change in V
• Constant P 1st law?


  Q = change in U + (px change in V)
• When cooling at a constant pressure, compression occurs. - Q - w and - U
• When heating at a constant pressure occurs, expansion occurs. + Q + W + U
• Cooking at constant volume - Q W= 0 -U
• Heating at constant volume + Q + U
• Qh is the energy from external heat
• Isothermal processes are difficult to achieve as would have to move very slowly (especially for engines)