Equation explained

where P_ext is the external pressure, and 🔺V is the change in volume. A classic example of this is a piston. As heat is added to the cylinder, the pressure inside the cylinder increases. The piston then rises to relieve the pressure difference between the pressure inside the cylinder and the external pressure. By increasing the volume in the cylinder, the piston has just done work. Reference the picture below.

The sum of heat and work is the change in internal energy, Δ U .

In an isolated system, q = − w . Therefore, Δ U = 0 .

In quantum mechanics, the equation

• H^ψn=Enψn

Where,

• E = the energy corresponding to a wave function
• V = the potential
• H^ = the Hamiltonian operator

The equation is analogous to the equation:

E=T+V