January 29AP Physics

Gateway High School Olycasts

IN A gas follows the

cycles shown. How much work is done?

Objective:

To find out how the conservation of energy applies to thermodynamics

Homework check

Conservation of Energy

ΔPE + ΔKE + ΔU = 0

James Prescott Joule

Work in thermodynamic processes

W=FΔd

W=PAΔd

W= -PΔV

PV diagram

First law of Thermodynamics

ΔU = Q + W

Isovolumetric (volume constant)

ΔU = Q

Isothermal (temperature constant)

ΔU = 0

Therefore

Q = W

Isobaric (pressure constant)

ΔU = Q + W

Adiabatic (thermally isolated system)

ΔU = W

Process conditions first law

Isobaric both temp ΔU=Q+Wand volume change

Isovolumetric no work ΔV=0 so W=0so ΔU=Q

Isothermal no change ΔU=Q+W=0

in T or U so Q= - WAdiabatic no energy Q=0

transfer as so ΔU=Wheat

PV diagrams and thermodynamic processes (quick quiz 12.2)

Identify the paths

Problems

White board these problems together:

50, 51, 54

Out:

Which of these processes are isothermal, isovolumetric, or adiabatic:

a) A tire being rapidly inflated

b) A tire expanding gradually at a constant temperature

c) A steel tank of gas being heated