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What is the Work Done in an Isobaric Process?
Grade Level:
Class 12
AI/ML, Physics, Biotechnology, FinTech, EVs, Space Technology, Climate Science, Blockchain, Medicine, Engineering, Law, Economics
Definition
What is it?
Work done in an isobaric process is the energy transferred when a gas expands or compresses while its pressure remains constant. Imagine blowing up a balloon; the pressure inside stays roughly the same as it gets bigger, and that expansion involves work.
Simple Example
Quick Example
Think about a pressure cooker on a stove. As the water inside heats up and turns into steam, the volume of the steam increases, pushing against the lid. If the pressure inside the cooker stays constant (which it does until the whistle blows), the work done by the steam in pushing the lid up slightly is an example of work done in an isobaric process.
Worked Example
Step-by-Step
QUESTION: A gas expands at a constant pressure of 200,000 Pascals (Pa) from an initial volume of 0.05 cubic meters (m^3) to a final volume of 0.15 cubic meters (m^3). Calculate the work done by the gas.
STEP 1: Identify the given values.
Pressure (P) = 200,000 Pa
Initial Volume (V_initial) = 0.05 m^3
Final Volume (V_final) = 0.15 m^3
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STEP 2: Recall the formula for work done in an isobaric process.
Work Done (W) = P * (V_final - V_initial)
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STEP 3: Calculate the change in volume (delta V).
delta V = V_final - V_initial = 0.15 m^3 - 0.05 m^3 = 0.10 m^3
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STEP 4: Substitute the values into the formula.
W = 200,000 Pa * 0.10 m^3
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STEP 5: Perform the multiplication.
W = 20,000 Joules (J)
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ANSWER: The work done by the gas is 20,000 Joules.
Why It Matters
Understanding work done in isobaric processes is crucial for engineers designing engines and power plants, like those used in EVs. It helps in optimizing how efficiently energy is converted. Climate scientists use this to model atmospheric changes, and it's key for biotechnologists working with controlled environments.
Common Mistakes
MISTAKE: Using the initial or final volume directly instead of the change in volume. | CORRECTION: Always calculate the difference between the final and initial volumes (delta V) before multiplying by pressure.
MISTAKE: Forgetting that if the gas is compressed (volume decreases), the work done by the gas is negative. | CORRECTION: Remember that work done BY the gas is positive for expansion and negative for compression. If volume decreases, (V_final - V_initial) will be negative, making W negative.
MISTAKE: Using inconsistent units, like pressure in atmospheres and volume in cubic centimeters. | CORRECTION: Always convert all units to SI units (Pascals for pressure, cubic meters for volume) before calculation to get work done in Joules.
Practice Questions
Try It Yourself
QUESTION: A balloon expands from 2 cubic meters to 5 cubic meters at a constant pressure of 100,000 Pa. How much work is done by the gas? | ANSWER: 300,000 Joules
QUESTION: A gas is compressed from 0.8 m^3 to 0.3 m^3 under a constant pressure of 150 kPa. Calculate the work done by the gas. (Hint: 1 kPa = 1000 Pa) | ANSWER: -75,000 Joules
QUESTION: A piston in an engine moves such that the volume of the gas changes by 0.025 m^3. If the constant pressure during this process is 300,000 Pa and the work done by the gas is 7500 J, did the gas expand or compress? Justify your answer. | ANSWER: The gas expanded. Since the work done (W) is positive (7500 J) and W = P * delta V, and P is always positive, delta V must also be positive. A positive delta V means V_final > V_initial, which indicates expansion.
MCQ
Quick Quiz
Which of the following describes an isobaric process?
Temperature remains constant
Volume remains constant
Pressure remains constant
No heat is exchanged
The Correct Answer Is:
C
An isobaric process is defined by constant pressure. The other options describe isothermal (constant temperature), isochoric (constant volume), and adiabatic (no heat exchange) processes, respectively.
Real World Connection
In the Real World
In a diesel engine, during the power stroke, hot gases expand and push the piston down. If we simplify this, the expansion can be considered an isobaric process for a short duration, where the constant pressure of the burning fuel-air mixture does work on the piston, making the vehicle move. This concept is vital for designing efficient engines for cars and trucks that we see on Indian roads.
Key Vocabulary
Key Terms
ISOBARIC PROCESS: A thermodynamic process where the pressure of the system remains constant | PASCAL (Pa): The SI unit of pressure | JOULE (J): The SI unit of work and energy | EXPANSION: When the volume of a gas increases | COMPRESSION: When the volume of a gas decreases
What's Next
What to Learn Next
Next, you should explore 'Work Done in Isothermal and Adiabatic Processes'. This will help you understand how work is calculated when temperature or heat exchange changes, building on your knowledge of constant pressure processes.
