List of top Physics Questions on Thermal Physics asked in JEE Main

The heat extracted out of \( x \) gram of water initially at \( 50^\circ\text{C} \) to cool it down to \( 0^\circ\text{C} \) is sufficient to evaporate \( (1000-x) \) gram of water also initially at \( 50^\circ\text{C} \). The value of \( x \) (closest integer) is \dots
(Take latent heat of water 2256 kJ/kg, specific heat capacity of water 4200 J/kg$\cdot$K)}

The temperature of a metal strip having coefficient of linear expansion $\alpha$ is increased from $T_1$ to $T_2$ resulting in increase of its length by $\Delta L_1$. The temperature is further increased from $T_2$ to $T_3$ such that the increase in its length is $\Delta L_2$.
Given $T_3 + T_1 = 2T_2$ and $T_2 - T_1 = \Delta T$, the value of $\Delta L_2$ is ________.

Two cars A & B are moving on a road with speed 100 km/hr and 80 km/hr. A stone is thrown from car B with speed \( V \) km/hr relative to it. Stone hits the car A with speed 5 m/s with respect to car A (ignore gravity). The value of \( V \) is: [All given velocities are in the same direction]

Statement-1: Two gases \( \mathrm{H_2} \) and \( \mathrm{O_2} \) are having the same average kinetic energy, then they have the same temperature.
Statement-2: \( \mathrm{H_2} \) and \( \mathrm{O_2} \) will have the same \( v_{\mathrm{rms}} \) at the same temperature.

For a concave mirror of focal length 10cm, magnification is 2 for two positions of an object. Find the distance between these two positions (in cm).

Two particles of the same masses moving initially with velocity \( 4 \hat{i} \) and \( 4 \hat{j} \) m/s respectively.
Acceleration of the first particle is \( 6 \hat{i} + 6 \hat{j} \) and of the second is zero. Find the path of the center of mass of the system.

In YDSE, intensity of both coherent sources are \(I_0\). Separation between the two slits is 5 cm and screen is placed at a distance of 50 cm from the slit. Wavelength of light is 6000 \(\text{Å}\). If intensity for a point on the screen is \(I_0\), then find the path difference at point P.

If \(x\) gm of water at \(50^\circ\text{C}\) cools to \(0^\circ\text{C}\), the heat released is \(H\). If \((100 - x)\) gm of water at \(50^\circ\text{C}\) is completely vapourised, the heat required is also \(H\). Find \(x\).

Identify correct statements (1) Zeroth law of thermodynamics gives concept of temperature. (2) In isothermal expansion \(\Delta Q \neq \Delta W\). (3) First law of thermodynamics gives concept of internal energy. (4) Product of intensive and extensive properties is extensive. (5) Ratio of extensive property and mass is extensive.

For ideal gas: \(n\): number of moles, \(C_v\): molar specific heat at constant volume, \(\gamma\): adiabatic exponent of gas, \(T_f\): final temperature, \(T_i\): initial temperature, \(R\): gas constant. Assertion : \[ nC_v(T_f-T_i)=\frac{nR}{\gamma-1}(T_f-T_i) \] Reason : \[ \gamma = 1 + \frac{2}{f} \]

Two rods of equal length 60 cm each are joined together end to end. Coefficient of linear expansions of the rods are \( 24 \times 10^{-6} \, \text{°C}^{-1} \) and \( 1.2 \times 10^{-5} \, \text{°C}^{-1} \). Their temperatures are the same and equal to \( 30^\circ \text{C} \), which is increased to \( 100^\circ \text{C} \). Find final length of the combination (in cm).