Advertisements
Advertisements
प्रश्न
derive the relation between the change in internal energy (∆U), work is done (W), and heat (Q).
Advertisements
उत्तर
Relation between the change in internal energy (ΔU), work is done (W), and heat (Q):
- When the amount of heat Q is added to the system and the system does not do any work during the process, its internal energy increases by the amount, ΔU = Q.
- When the system does some work to increase its volume, and no heat is added to it while expanding, the system loses energy to its surrounding,s and its internal energy decreases.
∴ ΔU = –W. - As the internal energy can be changed using both ways, we can consider the total change in the internal energy as,
ΔU = Q – W ….(1)
This is the mathematical statement of the first law of thermodynamics.
APPEARS IN
संबंधित प्रश्न
Explain why Air pressure in a car tyre increases during driving.
A steam engine delivers 5.4×108 J of work per minute and services 3.6 × 109 J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?
Should the internal energy of a system necessarily increase if heat is added to it?
The outer surface of a cylinder containing a gas is rubbed vigorously by a polishing machine. The cylinder and its gas become warm. Is the energy transferred to the gas heat or work?
Can work be done by a system without changing its volume?
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 ?
When a tyre bursts, the air coming out is cooler than the surrounding air. Explain.
Figure shows two processes A and B on a system. Let ∆Q1 and ∆Q2 be the heat given to the system in processes A and B respectively. Then ____________ .
Refer to figure. Let ∆U1 and ∆U2 be the changes in internal energy of the system in the process A and B. Then _____________ .
Consider two processes on a system as shown in figure.
The volumes in the initial states are the same in the two processes and the volumes in the final states are also the same. Let ∆W1 and ∆W2 be the work done by the system in the processes A and B respectively.
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.
A mixture of fuel and oxygen is burned in a constant-volume chamber surrounded by a water bath. It was noticed that the temperature of water is increased during the process. Treating the mixture of fuel and oxygen as the system,
- Has heat been transferred?
- Has work been done?
- What is the sign of ∆U?
Which of the following is correct, when the energy is transferred to a system from its environment?
Which of the following system freely allows the exchange of energy and matter with its environment?
What is the energy associated with the random, disordered motion of the molecules of a system called as?
Define heat.
Explain given cases related to energy transfer between the system and surrounding –
- energy transferred (Q) > 0
- energy transferred (Q) < 0
- energy transferred (Q) = 0
The internal energy of a system is ______
In a thermodynamic system, working substance is ideal gas. Its internal energy is in the form of ______.
When 1 g of water at 0° C and 1 x 105 N/m2 pressure is converted into ice of volume 1.082 cm3, the external work done will be ____________.
Two samples A and B, of a gas at the same initial temperature and pressure are compressed from volume V to V/2; A isothermally and B adiabatically. The final pressure of A will be ______.
In thermodynamics, heat and work are ______.
If a gas is compressed adiabatically:
The internal energy of one mole of argon is ______.
Explain the change in internal energy of a thermodynamic system (the gas) by heating it.
