Laws of Thermodynamics Physics - Laws of Thermodynamics

A gas is contained in a metallic cylinder fitted with a piston. The piston is suddenly moved in to compress the gas and is maintained at this position. As time passes the pressure of the gas in the cylinder:

1. Increases.
2. Decreases.
3. Remains constant.
4. Increases or decreases depending on the nature of the gas.

The first law of thermodynamics is a statement of:

1. Conservation of heat.
2. Conservation of work.
3. Conservation of momentum.
4. Conservation of energy.

An ideal gas goes from the state i to the state fas shown in figure. The work done by the gas during the process:

1. Is positive.
2. Is negative.
3. Is zero.
4. Cannot be obtained from this information.

The internal energy of an ideal gas decreases by the same amount as the work done by the system:

1. The process must be adiabatic.
2. The process must be isothermal.
3. The process must be isobaric.
4. The temperature must decrease.

In a process on a system, the initial pressure and volume are equal to the final pressure and volume.

1. The initial temperature must be equal to the final temperature.
2. The initial internal energy must be equal to the final internal energy.
3. The net heat given to the system in the process must be zero.
4. The net work done by the system in the process must be zero.

Should the internal energy of a system necessarily increase if its temperature is increased?

Can work be done by a system without changing its volume?

A gas is enclosed in a cylindrical vessel fitted with a frictionless piston. The gas is slowly heated for some time. During the process, 10J of heat is supplied and the piston is found to move out 10cm. Find the increase in the internal energy of the gas. The area of cross section of the cylinder = 4cm² and the atmospheric pressure = 100kPa.

The pressure of a gas changes linearly with volume from 10kPa, 200cc to 50kPa, 50cc.

1. Calculate the work done by the gas.
2. If no heat is supplied or extracted from the gas, what is the change in the internal energy of the gas?

An ideal gas is taken from an initial state i to a final state f in such a way that the ratio of the pressure to the absolute temperature remains constant. What will be the work done by the gas?

A force F is applied on a block of mass M. The block is displaced through a distance d in the direction of the force. What is the work done by the force on the block? Does the internal energy change because of this work?

When we stir a liquid vigorously, it becomes warm. Is it a reversible process?

Calculate the change in internal energy of a gas kept in a rigid container when 100J of heat is supplied to it.

Figure. shows three paths through which a gas can be taken from the state A to the state B. Calculate the work done by the gas in each of the three paths.

What should be the condition for the efficiency of a Carnot engine to be equal to 1?

A substance is taken through the process abc as shown in figure. If the internal energy of the substance increases by 5000J and a heat of 2625cal is given to the system, calculate the value of J.

When a tyre bursts, the air coming out is cooler than the surrounding air. Explain.

When we rub our hands they become warm. Have we supplied heat to the hands?

An ideal gas is pumped into a rigid container having diathermic walls so that the temperature remains constant. In a certain time interval, the pressure in the container is doubled. Is the internal energy of the contents of the container also doubled in the interval?

A closed bottle contains some liquid. The bottle is shaken vigorously for 5 minutes. It is found that the temperature of the liquid is increased. Is heat transferred to the liquid? Is work done on the liquid? Neglect expansion on heating.

Figure. shows the variation in the internal energy U with the volume V of 2.0mol of an ideal gas in a cyclic process abcda. The temperatures of the gas at b and c are 500K and 300K respectively. Calculate the heat absorbed by the gas during the process.

The internal energy of a gas is given by U = 1.5PV. It expands from 100cm³ to 200cm³ against a constant pressure of 1.0 x 10⁵Pa. Calculate the heat absorbed by the gas in the process.

A gas is taken through a cyclic process ABCA as shown in figure. If 2.4 cal of heat is given in the process, what is the value of J?

Figure. shows a paddle wheel coupled to a mass of 12kg through fixed frictionless pulleys. The paddle is immersed in a liquid of heat capacity 4200JK^-1 kept in an adiabatic container. Consider a time interval in which the 12kg block falls slowly through 70cm.

1. How much heat is given to the liquid?
2. How much work is done on the liquid?
3. Calculate the rise in the temperature of the liquid neglecting the heat capacity of the container and the paddle.

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Figure. shows a cylindrical tube of volume V with adiabatic walls containing an ideal gas. The internal energy of this ideal gas is given by 1.5nRT. The tube is divided into two equal parts by a fixed diathermic wall. Initially, the pressure and the temperature are P₁, T₁ on the left and p₂, T₂ on the right. The system is left for sufficient time so that the temperature becomes equal on the two sides.

1. How much work has been done by the gas on the left part?
2. Find the final pressures on the two sides.
3. Find the final equilibrium temperature.
4. How much heat has flown from the gas on the right to the gas on theleft?