Application of the first law of thermodynamics to isoprocesses Summary table

APPLICATION OF 1 LAW OF THERMODYNAMICS TO ISOPROCESSES

Process

Constant

m=const

M=const

Graph

Change in

internal

energy

Record

1st law

thermodynamics

Physical

meaning

Isothermal

expansion

T=const

pV=const

U=const

ΔU=0

Q=A'

An isothermal process cannot occur without heat transfer. All the amount of heat transferred to the system is expended on the performance of mechanical work by this system.

Isothermal

compression

T=const

pV=const

U=const

ΔU=0

A=-Q

An isothermal process cannot occur without heat transfer.

All work of external forces is emitted in the form of heat.

Isochoric

the heating

V=const

p↑

T↑

U↑

ΔU>0

A=0

Q= ΔU

All the amount of heat transferred to the system is spent on increasing its internal energy.

Isochoric

cooling

V=const

p↓

T↓

U↓

ΔU<0

A=0

Q= ΔU<0

The system reduces its internal energy, giving off heat to surrounding bodies.

Isobaric

expansion (heating)

p=const

V­↑

T­↑

U­↑

ΔU>0

Q=ΔU+A'

ΔU=Q-А'>0

The amount of heat transferred to the system exceeds the perfect mechanical work. Part of the heat is spent on the work, and some - to increase the internal. energy.

Isobaric

compression (cooling)

p=const

V↓

T↓

U↓

ΔU<0

ΔU=Q+A<0

Q<0

The amount of heat given by the system exceeds the work of external forces. Part of the heat the system gives by reducing the internal. energy.

Adiabatic

Expansion

=const

ΔU<0

U↓

 T↓

Q=0

A' > 0

ΔU=-A' < 0

A'=-ΔU

The system performs mechanical work only by reducing its internal energy.

Adiabatic

compression

=const

ΔU>0

U­↑

 T­↑

Q=0

A>0

ΔU=A

The internal energy of the system increases due to the work of external forces.