Quiz — The First Law of Thermodynamics

Question 1

Why do we write δQ and δW rather than dQ and dW?

Accepted Answer

Because they are inexact differentials: their integrals depend on the path followed.

Question 2

A closed system undergoes a cyclic transformation (A → A). What can we say about the balance Q_cycle + W_cycle?

Accepted Answer

It is zero because U is a state function.

Question 3

A gas is compressed quasi-statically. What can we say about the work received by the gas?

Accepted Answer

It is positive: the gas receives work during compression.

Question 4

During an isochoric transformation of a closed system, with pressure-volume work as the only form of work, we always have:

Accepted Answer

W = 0, so ΔU = Q