Question 97: Thermodynamics & KTG

Question

The figure shows the PV plot of an ideal gas taken through a cycle ABCDA. The part ABC is a semicircle and CDA is half of an ellipse. Then,

Accepted Answer

We observe the following:
$$\bullet$$ For the path B $$	o$$ C $$	o$$ D, the volume (V) decreases; $$\Delta$$W < 0.
$$\Delta U < 0 \Rightarrow \Delta Q < 0$$
$$\bullet$$ For the process A $$	o$$ B $$	o$$ C, $$\Delta$$W is the area of the semicircle and $$\Delta W 
e 0$$.
$$\bullet$$ For the process A $$	o$$ B (semicircle), it cannot be an isothermal process (whose PV-diagram is a rectangular hyperbola).
$$\bullet$$ For (clockwise) process A $$	o$$ B $$	o$$ C $$	o$$ D $$	o$$ A, $$\Delta$$W is the area enclosed, which is positive.

Answer

the process during the path A $$	o$$ B is isothermal.

Answer

heat flows out of the gas during the path B $$	o$$ C $$	o$$ D.

Answer

work done during the path A $$	o$$ B $$	o$$ C is zero.

Answer

positive work is done by the gas in the cycle ABCDA.

Thermodynamics & KTG

The figure shows the PV plot of an ideal gas taken through a cycle ABCDA. The part ABC is a semicircle and CDA is half of an ellipse. Then,

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