Q1. In a heat engine, if the input heat is 1000 J and the work done is 300 J, what is the efficiency of the engine?
Solution:
Efficiency is calculated as η = (Work output / Heat input) * 100%. Here, η = (300 J / 1000 J) * 100% = 30%.
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Q2. What is the term for the expansion of materials when heated?
Solution:
Thermal expansion refers to the increase in volume of materials when they are heated.
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Q3. What is the root mean square speed of nitrogen gas (N2) at 300 K? (Molar mass of N2 = 28 g/mol)
Solution:
The root mean square speed is given by the formula v_rms = sqrt(3RT/M), where R = 8.314 J/(mol·K), T = 300 K, and M = 0.028 kg/mol. v_rms = sqrt(3 * 8.314 * 300 / 0.028) ≈ 500 m/s.
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Q4. In an ideal gas, if the temperature is doubled while keeping the volume constant, what happens to the pressure?
Solution:
According to Gay-Lussac's law, pressure is directly proportional to temperature when volume is constant. Therefore, if the temperature is doubled, the pressure also doubles.
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Q5. What is entropy a measure of?
Solution:
Entropy is a measure of disorder or randomness in a system, indicating the number of ways a system can be arranged.
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Q6. What is the change in entropy when 1 kg of ice at -10°C is converted to water at 0°C?
Solution:
The change in entropy during the melting of ice is approximately 333 J/K.
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Q7. According to the kinetic theory of gases, what is the relationship between temperature and the average kinetic energy of gas molecules?
Solution:
The average kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas.
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Q8. What is the relationship between temperature and kinetic energy in gases?
Solution:
The average kinetic energy of gas molecules is directly proportional to the temperature of the gas.
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Q9. In a Carnot engine, if the hot reservoir is at 500 K and the cold reservoir is at 300 K, what is the maximum efficiency?
Solution:
The maximum efficiency of a Carnot engine is given by 1 - (T_c/T_h), which is 1 - (300/500) = 0.4 or 40%.
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Q10. In a heat engine, what is the purpose of the heat reservoir?
Solution:
The heat reservoir serves as a source of thermal energy that the heat engine absorbs heat from to perform work.
