Isothermal Process Slow Expansion

[Areena H 2K]

Why is the internal energy equal to 0 in an isothermal process (Q=W)?

[Hope Hyland 2D]

I think it's because if a process is isothermal, it means the temperature isn't changing, so there's essentially no transfer of heat, so q=0. Then, since q=w, as you stated, w also equals 0. Internal energy = q+w, so 0+0=0.

[Nathan Nakaguchi 1G]

For an isothermal process there is no addition or loss of energy, so the change in internal energy is 0.

Since delta U = q +w and the definition of isothermal is no addition or loss of energy from the surroundings 0 = q + w.

Doing some algebra can yield q = -w (remember that usually work= -number, already so you'll be doing negative times a negative)