The first law of thermodynamics gives the mathematical relation between
Answers
Answer:
The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is ΔU = Q − W. ... So positive Q adds energy to the system and positive W takes energy from the system.
Answer:
What is the First Law of Thermodynamics?
First Law of Thermodynamics thermodynamic system in an equilibrium state possesses a state variable known as the internal energy(E). Between two systems the change in the internal energy is equal to the difference of the heat transfer into the system and the work done by the system.
The first law of thermodynamics states that the energy of the universe remains the same. Though it may be exchanged between the system and the surroundings, it can’t be created or destroyed. The law basically relates to the changes in energy states due to work and heat transfer. It redefines the conservation of energy concept.
First Law of Thermodynamics
The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.
To help you understand the meaning of the First Law, we can take the common example of a heat engine. In a Heat engine, the thermal energy is converted into mechanical energy and the process also is vice versa. Heat engines are mostly categorized as an open system. The basic working principle of a heat engine is that it makes use of the different relationships between heat, pressure and volume of a working fluid which is usually a gas. Sometimes phase changes might also occur involving a gas to liquid and back to gas.
First Law of Thermodynamics Equation
The equation for the first law of thermodynamics is given as;
ΔU = q + W
Where,
ΔU = change in internal energy of the system.
q = algebraic sum of heat transfer between system and surroundings.
W = work interaction of the system with its surroundings.
First Law of Thermodynamics Equation
Points to Remember
For an isolated system, energy (E) always remains constant.
Internal Energy is a point function and property of the system. Internal energy is an extensive property (mass-dependent) while specific energy is an intensive property (independent of mass).
For an ideal gas, the internal energy is a function of temperature only.
Some Examples:
Q. A gas has constant pressure in a system. There is a loss of 45 J of heat in the surroundings around the system. 450 J of work is done onto the system. Find the system’s internal energy?
Solution:
ΔU = q+w
ΔU = 45J + 450J
ΔU = 495J
In general, if we want to find the internal energy which is denoted by ΔU, it is important to consider the relationship between the surroundings and the system. We already know according to the law that energy is neither created nor destroyed. Thus, we can tell that anything that is lost by the surroundings will be gained by the system. Moreover, the surrounding area will lose heat and carry out some work onto the system. So if we look at q and w they are positive in the equation and this is mainly due to the system gaining some heat and work being done on itself.