First Law of Thermodynamics

First Law of Thermodynamics
or
The Conservation of Energy

The net amount of energy added to a system (in the form of heat or work) = net increase in the energy stored internally in the system plus any change in the mechanical energy of system's center of mass .

U	= Internal Energy of the System (SI: J)
W	= Work done by or on the System (SI: J)
Q	= Heat flow in or out of the System (SI: J)
ME_cm	= Mechanical Energy of the center-of-mass (SI: J) = KE_cm + PE_cm + RE_cm

* For systems where the change in mechanical is unimportant, the first law of thermodynamics is written as:

It is important to observe that the Δ in ΔU is absolutely necessary because both work W and heat Q represent a transfer of energy where as the internal energy U is a quantity of energy that a system contains.

The quantities Q_in, Q_out, W_in, and W_out are all taken to be positive quantities where as Q and W can be either positive or negative.

Relationship between Work, Heat and Internal Energy

First Law of Thermodynamics or The Conservation of Energy

First Law of Thermodynamics
or
The Conservation of Energy