Class 11 NEET Physics Thermodynamics and Kinetic Theory

Concept:According to the First Law of Thermodynamics for an isothermal process involving an ideal gas, the heat supplied to the system is equal to the work done by the system.Explanation:1. An isothermal process occurs at a constant temperature ($\Delta T = 0$).2. For an ideal gas, the internal energy ($U$) is a function of temperature only. Therefore, the change in internal energy is zero ($\Delta U = 0$).3. The First Law of Thermodynamics states: $\Delta Q = \Delta U + \Delta W$.4. Substituting $\Delta U = 0$, we get $\Delta Q = \Delta W$.5. The problem states the gas undergoes an *expansion*. During expansion, the gas does positive work on its surroundings. The phrase "does -150 J of work" implies the work done *on* the gas is -150 J, which means the work done *by* the gas is $\Delta W = +150$ J.6. Therefore, the heat supplied to the gas is $\Delta Q = \Delta W = +150$ J. The positive sign indicates that heat is added to the gas.Answer:D. 150 J of heat has been added to the gas