List of top Physics Questions on Thermodynamics

Two gases A and B are filled at the same pressure in separate cylinders with movable pistons of radii \(r_A\) and \(r_B\) respectively. On supplying an equal amount of heat to both the cylinders, their pressures remain constant and their pistons are displaced by 16 cm and 9 cm respectively. If the change in their internal energies is the same, then the ratio \(r_A / r_B\) is:

In adiabatic compression, which of the following is true?

An ideal gas undergoes an adiabatic expansion from volume \( V \) to \( 2V \). If the initial temperature is \( T \), what is the final temperature? (Assume the ratio of specific heats \( \gamma = \frac{5}{3} \))

The rate constant $ k $ of a reaction doubles when the temperature is raised from 300 K to 310 K. Calculate the activation energy $ E_a $ of the reaction. (Use $ R = 8.314 \, J/mol\cdot K $)

How much heat is required to raise the temperature of $ 2 \, kg $ of water from $ 20^\circ C $ to $ 80^\circ C $? (Specific heat capacity of water = $ 4200 \, J/kg^\circ C $)

The internal energy of a thermodynamic system is given by \( U = a s^{4/3} v^\alpha \), where \( s \) is entropy, \( v \) is volume, and \( a \) and \( \alpha \) are constants. The value of \( \alpha \) is:

According to the law of equipartition of energy, the number of vibrational modes of a polyatomic gas of constant \(\gamma = \frac{C_P}{C_V}\) is (\(C_P\) where \(C_V\) are the specific heat capacities of the gas at constant pressure and constant volume, respectively):

The value of electric potential at a distance of 9 cm from the point charge \(4 \times 10^{-7} \, \text{C}\) is
\[ \text{Given} \, \frac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \, \text{N m}^2 \text{C}^{-2} \]

Water is used as a coolant in a nuclear reactor because of its

A thermodynamic system is taken through the cycle abcda. The work done by the gas along the path bc is :

A cylinder of fixed capacity \( 67.2 \, \mathrm{L} \) contains helium gas at STP. The amount of heat needed to raise the temperature of the gas in the cylinder by \( 20^\circ \mathrm{C} \) is:

If \( \mathbf{A} = 4\hat{i} + 3\hat{j} \) and \( \mathbf{B} = 3\hat{i} + 4\hat{j} \), then the cosine of the angle between \( \vec{A} \) and \( \vec{A} + \vec{B} \) is:

The output \( Y \) of the following logic circuit for given inputs is: 

A current of 10 A exists in a wire of cross-sectional area of \( 5 \times 10^{-6} \, \text{m}^2 \) with a drift velocity of \( 2 \times 10^{-3} \, \text{m/s} \). The number of free electrons in each cubic meter of the wire is: