Thermodynamics

Question 1

What is work done on gas at constant pressure?

Answer 1

W = -PdeltaV

Question 2

What is the formula for area on PV diagram?

Answer 2

A = PdeltaV = work done on gas

Question 3

What is the first law of thermodynamics?

Answer 3

delta U = Q + W

Question 4

What is internal energy of ideal gas?

Answer 4

delta U = nCvdeltaT

Question 5

What is Cv?

Answer 5

Molar specific heat at constant volume
3/2R = monoatomic gas
5/2R = diatomic gas

Question 6

What are the thermal process in gases?

Answer 6

Isobaric (constant pressure)
Isovolumetric (constant volume, W = 0)
Adiabatic (no thermal energy transfer, Q = 0)
Isothermal (constant temperature, delta U = 0)

Question 7

What is cyclic process?

Answer 7

Energy transferred by heat from a source of high temperature.
Work done by the engine.
Energy is expelled from the engine by heat to a source of low temperature.

Question 8

What is reversible process?

Answer 8

Every state along the path is in equilibrium state.
can return to original condition by going in reverse.

Question 9

Talk about Carnot cycle.

Answer 9

Isothermal expansion at Th in which the gas is in thermal contact with hot reservoir at Th.
Absorbs energy Qh and does work WAB in raising the piston.
Base replaced by thermal nonconducting wall and gas expands adiabatically. No energy leaves or enter system by heat. Th becomes Tc and gas does work WBC to raise piston.
Gas placed thermal contact with cold reservoir at Tc and compressed isothermally at Tc. Gas expels energy Qc to reservoir and work WCD done on gas.
Base again replaced with thermal nonconducting wall and gas compressed adiabatically. Temperature increase to Th and work WDA done on gas.