# What is Principle of Conservation of Energy? – Definition and Limitations

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Before getting into the specifics of the principle of conservation of energy, let’s first understand some basic concepts about energy. Energy is the ability to perform work. It could exist in several forms, such as potential, kinetic, thermal, electrical, chemical, and radioactive. Also, there is heat and work, and energy is transferred from one body to another. Energy is always assigned based on its nature once it has been transmitted. Thus, heat transmitted may manifest as thermal energy, while work performed may result in mechanical energy.

According to the principle of conservation of energy, energy can change its form but cannot be created or destroyed. The joule is the unit of measurement for energy in the International System of Units (SI), which is defined as “the energy transmitted to an object by the effort of moving it a distance of one meter against a force of one Newton”. Let us now take a deep dive into the concepts of the principle of conservation of energy.

## What is the Principle of Conservation of Energy?

This concept states that energy cannot be generated or destroyed but can only be converted or moved from one form to another. Emilie du Chatelet initially proposed and tested the principle of conservation of energy.

### State Principle of Conservation of Energy

According to the principle of conservation of energy, the overall energy of an isolated system stays constant over time.

For instance, when a stick of dynamite explodes, chemical energy is transformed into kinetic energy. The exact drop-in chemical energy in the dynamite’s combustion can be calculated by adding up all the energies released during the explosion, including the kinetic and potential energy of the fragments, heat, and sound.

### State the Principle of Conservation of Mechanical Energy

The principle of conservation of mechanical energy states that “The total mechanical energy of a system is conserved, meaning it cannot be generated or destroyed and can only change internally from one form to another when conservative forces are acting on the system.”

## First Law of Thermodynamics

Internal energy is a state variable that exists in a thermodynamic system at equilibrium (E). The difference in heat transfer into and work performed by two systems is equal to the change in internal energy between the two systems.

The universe’s energy is constant, according to the principle of conservation of energy. It cannot be created or destroyed but can be exchanged between the system and its surroundings. The law essentially deals with how work and heat transport cause changes in energy states. It redefines the idea of energy conservation.

“According to the First Law of Thermodynamics, heat is a type of energy, and as a result, thermodynamic processes are governed by the idea of energy conservation. In other words, heat energy cannot be produced or destroyed. But it can be moved from one place to another and changed into and out of various types of energy.”

### The Equation for the First Law of Thermodynamics

The first law of thermodynamics equation is as follows:

ΔU = q + W

Where,

• ΔU = system’s internal energy change.
• q is the algebraic sum of heat transmission from the system to its surroundings.
• W stands for the system’s interaction with its environment.

## Principle of Conservation of Energy Examples

A bicycle pump is a good example of the principle of energy conservation. It gets heated when we pump the handle quickly because the gas undergoes mechanical action, which increases its internal energy. In the case of a bicycle pump with a blocked outlet, that makes it possible to keep track of the air temperature.

The thermometer registers a temperature rise when the piston is moved swiftly because the air’s internal energy has increased. The air is affected by the push force, which results in an increase in internal energy and a corresponding temperature rise.

## Limitations of the Principle of Conservation of Energy

The principle of conservation of energy is stated in the first law. The first law’s fulfillment alone does not guarantee that the process will occur. This law, however, has various limitations, some of which are listed below.

• The first law of thermodynamics has a drawback: it says nothing about the direction of heat flow.
• Whether the process is spontaneous or not is not stated.
• The process cannot be reversed. In reality, not all of the heat is converted into work. We could have driven ships across the ocean by drawing heat from the ocean’s water if it had been possible to transform all of the heat into work.
POPULAR EXAMS
SSC and Bank
Other Exams
GradeStack Learning Pvt. Ltd.Windsor IT Park, Tower - A, 2nd Floor, Sector 125, Noida, Uttar Pradesh 201303 help@byjusexamprep.com