Key Takeaways
Preparing for Class 12 Boards? This resource on Important conceptual questions of class 12 first law of thermodynamics includes PDF notes, past questions, and solutions. Updated for the 2081/2082 NEB syllabus, it covers all essential concepts in important_question to help you excel.
First law of thermodynamics
- Can the temperature of an isolated system changes?
Ans: Yes, in adiabatic process, the temperature of an isolated system changes. - When the air of the atmosphere rises up, it cools. Why?
Ans:When air rises, it expands due to decrease in the atmospheric pressure. As the expansion occurs in the air, it becomes cool. - What is the change in the internal energy of a gas which is compressed isothermally?
Ans: Internal energy is the function of temperature. During isothermal compression the temperature of the gas does not change. Therefore, the internal energy of the gas remains the same. - Ice at 0°C is heated to be converted into steam at 100°C. State the isothermal changes in the process of conversion of ice into stema.
Ans: In isothermal process, temperature remains constant. When ice melts at 0°C to water at 0°C and when water boils at 10°C to become steam at 100°C are the isothermal changes. - What happens to the air temperature in a valley when cold air blowing across the mountain tops descends into the valley?
Ans: As the cold air blowing across the mountain tops descends into the valley, it is adiabatically compressed. Consequently, the temperature in the valley is increased. - While stirring a liquid, it becomes warm. Is it reversible process?
Ans: While stirring a liquid some work is done on the system and it gets converted into heat. But, the heat cannot be converted back into the work. Hence it is not reversible process. - Can two isothermal curves intersect each other?
Ans: If two isothermal curves intersect each other, a gas will have the same values of pressure and volume at two different temperatures, which is imposssible. Hence, two isothermal curves do not intersect each other.