Key relationship
Φopen = EA cosθ; ∮E⃗·dA⃗ = qenc/ε₀.
Physics · Class 12
Electric flux and Gauss law
Tilt an open surface to change its projected area. Closed-surface flux instead depends on net enclosed charge; external charges contribute zero net closed flux.
Open the interactive experiment →Electric flux and Gauss law
திறந்த பரப்பின் மின்பாயம் EA cosθ. மூடிய பரப்பின் மொத்த பாயம் உள்ளடங்கிய மின்னூட்டத்தைச் சாரும்.
Key notes, relationships and model limits
Remember
Tilt an open surface to change its projected area. Closed-surface flux instead depends on net enclosed charge; external charges contribute zero net closed flux.
Common trap
A closed surface can have zero net flux while its local electric field is nonzero. Only enclosed charge fixes the net flux.
Model limits
Uniform field for the open plane; independent closed Gaussian surface with the specified net enclosed charge.
What you will learn
Use the controls and plotted relation to explain electric flux and gauss law.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
A 0.1 m² plane in 1000 N/C has flux 100 at 0° and zero at 90°.
Why this matters
The model connects electric flux and gauss law with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
A closed surface encloses zero net charge. Its net flux is?
- Zero only if E is zero everywhere on the surface.
- Zero, even if the field is nonzero at the surface.
- EA irrespective of the enclosed charge.
Read the explanation
Zero, even if the field is nonzero at the surface.
Course connection: Class XII Chapter 1. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.