Question 876: Thermodynamics & KTG

Question

A gas is compressed at a constant pressure of $$50 \mathrm{~N} / \mathrm{m}^2$$ from a volume of $$10 \mathrm{~m}^3$$ to a volume of $$4 \mathrm{~m}^3$$. Energy of $$100 \mathrm{~J}$$ is then added to the gas by heating. Its internal energy is

Accepted Answer

From first law of thermodynamics,
$$\mathrm{Q}=\Delta \mathrm{U}+\Delta \mathrm{W}=\Delta \mathrm{U}+\mathrm{P} \Delta \mathrm{V}$$
Change in volume due to compression
$$\Delta V=V_2-V_1=4-10=-6 m^3$$
Negative sign indicates gas is compressed.
$$	herefore \quad \Delta \mathrm{U}=\mathrm{Q}-\mathrm{P} \Delta \mathrm{V}=100-[50 	imes(-6)]=400 \mathrm{~J}$$
As, $$\Delta \mathrm{U}$$ is positive, the internal energy is increased.

Answer

increased by $$400 \mathrm{~J}$$

Answer

increased by $$200 \mathrm{~J}$$

Answer

increased by $$100 \mathrm{~J}$$

Answer

decreased by $$200 \mathrm{~J}$$

Thermodynamics & KTG

A gas is compressed at a constant pressure of $50 \mathrm{~N} / \mathrm{m}^2 from a volume of 10 \mathrm{~m}^3 to a volume of 4 \mathrm{~m}^3. Energy of 100 \mathrm{~J}$ is then added to the gas by heating. Its internal energy is

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