Change in entropy for certain processes (conceptual problem)

[joshuat]

Homework Statement

for change in entropy is it possible to have a process that is both adiabatic and irreversible?
is it possible for change in entropy to be reversible with heat transfer?
what are the changes in entropy if possible?
if you can answer please explain why

Homework Equations

S=Q/T

The Attempt at a Solution

adiabatic means no heat transfer. Irreversible means that there is friction in the process. Entropy is a thermodynamic property that is a measure of the energy not available for useful work.

for the first question I'm just wondering if friction is a form of heat transfer. I'm pretty sure it is so I want to say it is not possible.

for the second question i think it is nonzero. not sure if positive or negative. I think heat can be put in a system and then taken out while still remaining reversible.

 

[Mapes]

Hi joshuat, welcome to PF!

Irreversible means that there is friction in the process.

More generally, a process is irreversible if there's a difference in temperature, pressure, or any other intensive variable within the system. So consider a gas that's allowed to expand into a vacuum: we can insulate the system so that it's adiabatic, and the expansion into a larger space is certainly irreversible.

I think heat can be put in a system and then taken out while still remaining reversible.

Agreed, so long as the temperature difference is negligible.