Isobaric Process is a type of thermodynamic Process that involves constant pressure. The term isobaric is derived from Greek words “iso” and “baros”, which means equal pressure. Isobaric process results in work done when heat is transferred.

In this article, we will learn about the Isobaric Process, understand it with the help of an example, and others in detail.

What is Isobaric Process?

Isobaric process refers to constant pressure, when other factors like temperature or volume can change in a system. Let’s take one real-life example, imagine a soda can that is at normal room temperature. You put it inside the refrigerator for an hour. Throughout this process of changing the temperature of the soda, the pressure inside the soda can remains the same. Whenever pressure is constant and other factors change, we refer to it as an isobaric process.

Although temperature, volume, and internal energy may differ, pressure remains constant throughout the process. In equilibrium thermodynamics, which deals with the transfer of energy from one state to another, the Isobaric process plays a vital role in understanding the behavior to analyze any system.

Learn, Thermodynamics

Before learning about Isobaric Process let’s learn about What are Thermodynamic Process?

What are Thermodynamic Process?

A thermodynamic process is a process in which thermodynamic process such as Temperature, Pressure, and Volume changes with time. Various types of thermodynamic process are,

• Isothermal Process
• Isochoric Process
• Adiabatic Process

Isobaric Process Definition

In thermodynamics, when heat is converted to work keeping pressure constant is known as isobaric process. The work done is produced by the change in temperature, due to heat transfer and internal energy, throughout the process of state change is under constant pressure. This means that no quantities become zero, according to First Law of Thermodynamics.

An isobaric process is a type of thermodynamic process in which the pressure of the system stays constant, i.e.

ΔP = 0

Let us understand isobaric process using one example of temperature change, where pressure will be constant.

Isobaric Process Example

There are many examples of isobaric process, at an industrial level and in day-to day life. The best example can be the boiling water and how the state of water changes from one form to another. The atmospheric pressure on water remains constant, the increase in temperature of water leads to the transition of water to steam. Similar example is transition of Ice into Water. When we keep ice in room temperature, heat flows and results in melting of ice into water, while the atmospheric pressure remains constant.

Let us take another Example of Constant pressure, when we take a container filled with gas and close it with a piston which is allowed to move. As you heat the container, the temperature and volume will rise, keeping the pressure constant throughout the process.

Meaning of Isobaric Process

During Isobaric Process, pressure remains constant while other factors like temperature and volume tend to change. Constant pressure is the primary thing in this process which is achieved by exchanging energies. The system may absorb heat or release heat, which results in temperature change.

Numerically, this equation is represented using a formula, which can help in understanding and analyzing the system to make correct calculations and avoid failures. Let’s learn more about Isobaric Process Equation.

Isobaric Process Formula

Isobaric process formula follows Charles Law, which indicates that if pressure is constant, volume is directly proportional to temperature. Next, let us also understand relationship between various factors affecting the system while keeping pressure constant, Isobaric process follows first law of thermodynamics and ideal gas equation.

Isobaric Process Equation

As the pressure is constant, we observe that volume is directly proportional to temperature, we can solve it further using ideal gas law and first law of thermodynamics.

Isobaric process can be represented as first law of thermodynamics.

∆U = Q – P∆V

For gases, we can use ideal gas law,

PV = nRT

Work Done by a Gas in an Isobaric Process

The work done ny any gas in Isobaric Process is given by the formula added below,

Work done in Isobaric Process Formula

Work done is calculated using Pressure multiplied with change in volume of the system. The negative change in volume indicates compression in the system.

Work done is calculated using,

W = P∆V

P-V Diagram for Isobaric Process

P-V diagram for isobaric process is a horizontal straight line(representing constant pressure) parallel to volume axis. The direction of this line shows compression or expansion, which can also explain sign convention in work done(negative sign in compression), where area under this line shows the work done.

Isobaric Process

Difference between Isothermal and Isobaric Processes

Isothermal Process is also a type of thermodynamic process, where temperature remains constant while in isobaric process pressure remains constant throughout the process. Let us understand more difference in detail.

Learn more about, Difference Between Isothermal and Adiabatic Process

Difference between Adiabatic and Isobaric Processes

Both Isobaric and Adiabatic are types of thermodynamic process, they differ in factors affecting the system and hence the results are also affected. Isobaric is a process where pressure is constant while in adiabatic process, heat transfer in the system is not allowed. Knowledge about the difference of both process helps us analyze and understand the thermodynamic system better.

Reversible Isobaric Processes

Isobaric Process indicates a system in thermodynamics which undergoes changes when pressure is constant.

Work done formula of Reverse Isobaric Process,

W = P(V₁ – V₂)

where,

• P is Pressure
• V₁ is Initial Volume of System
• V₂ is Final Volume of System

Also, Check

• Thermodynamic Cycles
• Carnot Cycle

Examples on Isobaric Process

Example 1: During an isobaric expansion, a gas absorbs 100 J of heat and the pressure of gas is 10 atm. If the initial volume is 1 m³ and the final volume is 4 m³, find the change in internal energy.

Solution:

Given,

• Q = 100 J
• P = 10 atm
• V₁ = 1 m³
• V₂ = 4 m³

Change in internal energy U for an isobaric process is given by △U = Q – W

where, W = P(V₂ – V₁)

W = 10(4 – 1) = 10.3 = 30

△U = 100 – 30 = 70 J

Example 2: A gas undergoes an isobaric process, and its initial volume is 3m³. If the temperature increases from 300K to 450K, find the final volume.

Solution:

P is constant, since it is isobaric process.

Given,

• V₁ = 3 m³
• T₁ = 300 K
• T₂ = 450 K

Using Isobaric process equation V₁/T₁ = V₂/T₂

⇒ 3/300 = V₂/450

⇒ V₂ = 3 × 450/300 = 4.5m³

Example 3: A gas expands 0.25 m³ at constant pressure 10³ N/m², what is work done?

Solution:

Given,

• P = 1000 atm
• △ V = 0.25 m³

Work Done(W) = P △ V

W = 10³ × 0.25

W = 250 J

Example 4: A gas undergoes an isobaric compression, decreasing its volume from 8 m³ to 4 m³ under a constant pressure of 150 kPa. Determine the work done by the gas.

Solution:

W = P(V₂ – V₁)

W= 150 kPa × (4 – 8)

W = -600 kPa.m³

Note: Negative sign indicates work done during compression.

Example 5: A gas undergoes an isobaric process, expanding from an initial volume of 5 m³ to a final volume of 10m³ under a constant pressure of 200 Pa. Calculate work done by the gas during this process?

Solution:

W = P(V₂– V₁)

W = 200Pa × (10 – 5)

W = 200 × 5

W = 1,000 Pa.m³

Practice Questions on Isobaric Process

Q1: During an isobaric expansion, a gas absorbs 500 J of heat. if the initial volume is 10 m³ and the final volume is 40 m³, find the change in internal energy.

Q2: A gas undergoes an isobaric process, expanding from an initial volume of 58 m³ to a final volume of 190 m³ under a constant pressure of 200 Pa. Calculate work done by the gas during this process?

Q3: A gas undergoes an isobaric process, expanding from an initial volume of 67m³ to a final volume of 200m³ under a constant pressure of 200 Pa. Calculate work done by the gas during this process?

Q4: A gas expands 0.512 m³at constant pressure 983 N/m², what is work done?

Frequently Asked Questions on Isobaric Process

What is an Isobaric Process?

Isobaric Process is a type of thermodynamic system where pressure remains constant throughout the process, while temperature, internal energy and volume changes.

What are Types of Isobaric Process?

Isobaric Process is defined in two types

• Expansion
• Compression

How Can We Calculate Work Done During Expansion or Compression?

We can use work done formula for both expansion and compression, W = P.△ V

What is an Example of Isobaric Process?

Example of isobaric process is Water boiling and changing its state to gas (steam) under constant pressure.

What is Difference between Isochoric and Isobaric Process?

In Isochoric process Volume of the system remains constant throughout the process while in Isobaric process, pressure remains constant.

What are formulas for Isobaric Process?

Formulas for isobaric process are

• ΔU = ΔQ – ΔW
• ΔU = ΔQ – P(V₂ – V₁)