Change in the energy content of an isobaric process

[diaaa2]

Homework Statement

A PV diagram shows an isobaric expansion, I'm asked to know the signs of: work done on, heat added to, and change in energy content of the system.

Relevant Equations

W= integral (P dV), dU = Q + W

Homework Statement: A PV diagram shows an isobaric expansion, I'm asked to know the signs of: work done on, heat added to, and change in energy content of the system.
Homework Equations: W= integral (P dV), dU = Q + W

Since this is an expansion, the system does work on the surrounding and therefore the work done on the system is -ve.
Also, to preserve a constant pressure, heat has to be added, therefore heat added is +ve.

The energy content(dU) is the sum of those too, and since the process is isobaric not adiabatic, dU has a value.
How can I know whether it is negative or positive?

 

[kuruman]

What expression do you know for dU that involves the temperature change dT?

 

[vela]

The energy content(dU) is the sum of those too, and since the process is isobaric not adiabatic, dU has a value.

You should really write either $dU = dQ + dW$, if you're dealing with infinitesimal quantities, or $\Delta U = Q + W$, if not. I'll assume you really meant $\Delta U$, not $dU$.

$\Delta U$ is always going to have some value which depends only on where you start and where you end up, not the process, since $U$ is state variable.

Did you mean $\Delta U$ won't be 0? That claim would be true for both isobaric and adiabatic processes, so your logic doesn't make sense.