Physics 9702 · AS & A Level · The first law of thermodynamics

The first law of thermodynamics — practice question

A fixed mass of ideal gas occupies volume $V$ and has pressure $p$. The gas then completes the cycle X to Y to Z to X, as shown in Fig. 2.1. Table 2.1 gives the values of $p$, $V$ and temperature $T$ for the gas at points X, Y and Z.
(a)[1]

State the change in internal energy $\Delta U$ for one complete cycle, XYZ X. $\Delta U = \;\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\; \text{J}$

(b)[2]

Calculate the amount of gas $n$. $n = \;\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\; \text{mol}$

(c)[2]

Complete Table 2.1. Use the space below to show any working.

(d(i))[3]

The first law of thermodynamics for a system can be written as $\Delta U = q + W$. State, with reference to the system, the meaning of: $\Delta U:$ $q:$ $W:$

(d(ii))[2]

Explain the way in which the first law of thermodynamics applies to the change Z to X.

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