Thermal Physics - NEET Physics Questions
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Thermal Physics

Question 231: easy

A flask contains hydrogen and oxygen gas in the ratio of 3 : 1 by mass at temperature 27°C. The ratio of average translational kinetic energy per molecule of hydrogen and oxygen respectively is

1. 1 : 1
2. 3 : 1
3. 1 : 3
4. 1 : 4
View Answer

The average translational kinetic energy per molecule of any gas is given by \(\frac{3}{2} k_B T\). Since both gases are at the same temperature, the ratio of their translational kinetic energies is 1 : 1.

Question 232: easy

In winters, a metal surface feels cooler upon touching than a wooden surface because

1. Metal has high specific heat capacity as compared to wood
2. Wood has high specific heat capacity as compared to metal
3. Metal has high thermal conductivity
4. Metal has low thermal conductivity
View Answer

Metal is a much better conductor of heat than wood. When touched in winters, heat is rapidly conducted away from our hand to the metal surface, making it feel colder.

Question 233: easy

The internal energy of an ideal gas depends upon

1. Pressure
2. Temperature
3. Volume
4. Both (1) and (3)
View Answer

The internal energy of an ideal gas is a function of temperature only, as there are no intermolecular forces of attraction in an ideal gas. Therefore, \( U \propto T \).

Question 234: easy

A monoatomic gas does 150 J of work in isothermal expansion. The heat supplied to the gas is

1. 200 J
2. 150 J
3. 100 J
4. Zero
View Answer

For an isothermal process, the change in internal energy is \( \Delta U = 0 \). According to the first law of thermodynamics, \( Q = \Delta U + W \), which gives \( Q = 0 + 150\text{ J} = 150\text{ J} \).

Question 235: easy

For an ideal gas, total energy is equally distributed in all possible energy modes, with each mode has an average energy equal to \(\frac{1}{2} k_B T\), and each vibrational mode has energy contribution of

1. \(\frac{1}{3} k_B T\)
2. \(k_B T\)
3. \(\frac{3}{2} k_B T\)
4. \(\frac{1}{4} k_B T\)
View Answer

Each vibrational mode has both kinetic energy and potential energy modes, thus having two degrees of freedom. Therefore, the average energy per vibrational mode is \(2 \times \frac{1}{2} k_B T = k_B T\).

Question 236: easy

The relation between coefficient of linear expansion (\(\alpha\)) and coefficient of volume expansion (\(\gamma\)) for solids is

1. \(\gamma = 2\alpha\)
2. \(3\gamma = \alpha\)
3. \(\gamma = 3\alpha\)
4. \(2\gamma = 3\alpha\)
View Answer

Coefficient of volume expansion is three times the coefficient of linear expansion for an isotropic solid, i.e., \(\gamma = 3\alpha\).