# If ΔQ and ΔW represent the heat supplied to the system and  <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> the work done on the system, respectively, then the first law of thermodynamics can be written as: (where ΔU is the internal energy) 1. ΔQ = ΔU + ΔW 2. ΔQ = ΔU – ΔW 3. ΔQ = ΔW – ΔU 4. ΔQ = –ΔU – ΔW

Subtopic:  First Law of Thermodynamics |
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Can two isothermal curves cut each other?

 1 Never 2 Yes 3 They will cut when the temperature is 0°C. 4 Yes, when the pressure is equal to the critical pressure.
Subtopic:  Types of Processes |
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The latent heat of vaporisation of water is $$2240~\text{J/gm}$$. If the work done in the process of expansion of $$1~\text{g}$$ is $$168~\text{J}$$, then the increase in internal energy is:
1. $$2408~\text{J}$$
2. $$2240~\text{J}$$
3. $$2072~\text{J}$$
4. $$1904~\text{J}$$

Subtopic:  First Law of Thermodynamics |
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An ideal gas at $$27^{\circ}\mathrm{C}$$ is compressed adiabatically to $\frac{8}{27}$ of its original volume. If $\gamma =\frac{5}{3}$, then the rise in temperature will be:
1. 450 K
2. 375 K
3. 225 K
4. 405 K

Subtopic:  Types of Processes |
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A polyatomic gas $$\left(\gamma = \frac{4}{3}\right)$$ is compressed to $$\frac{1}{8}$$ of its volume adiabatically. If its initial pressure is $$P_0,$$ its new pressure will be:

 1 $$8P_0$$ 2 $$16P_0$$ 3 $$6P_0$$ 4 $$2P_0$$
Subtopic:  Types of Processes |
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A unit mass of a liquid with volume V1 is completely changed into a gas of volume V2 at a constant external pressure P and temperature T. If the latent heat of evaporation for the given mass is L, then the increase in the internal energy of the system is:
1.  Zero
2. $P\left({V}_{2}-{V}_{1}\right)$
3. $L-P\left({V}_{2}-{V}_{1}\right)$
4.  L

Subtopic:  First Law of Thermodynamics |
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An ideal heat engine working between temperatures T1 and T2 has an efficiency η. The new efficiency if both the source and sink temperatures are doubled will be:
1. $\frac{\eta }{2}$
2. η
3. 2η
4. 3η

Subtopic:  Carnot Engine |
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A monoatomic ideal gas, initially at temperature $$T_1$$, is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature $$T_2$$ by releasing the piston suddenly. If $$L_1$$ and $$L_2$$ are the lengths of the gas column before and after expansion, respectively, then $$\frac{T_1}{T_2}$$ is given by:
1. $$\left(\frac{L_1}{L_2}\right)^{\frac{2}{3}}$$
2. $$\frac{L_1}{L_2}$$
3. $$\frac{L_2}{L_1}$$
4. $$\left(\frac{L_2}{L_1}\right)^{\frac{2}{3}}$$

Subtopic:  Types of Processes |
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An insulator container contains 4 moles of an ideal diatomic gas at a temperature T. If heat Q is supplied to this gas, due to which 2 moles of the gas are dissociated into atoms, but the temperature of the gas remains constant, then:
1. Q = 2RT
2. Q = RT
3. Q = 3RT
4. Q = 4RT

Subtopic:  First Law of Thermodynamics |
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The volume of air (diatomic) increases by $$5\%$$ in its adiabatical expansion. The percentage decrease in its pressure will be:

 1 $$5\%$$ 2 $$6\%$$ 3 $$7\%$$ 4 $$8\%$$
Subtopic:  Types of Processes |
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