Electric Charges & Fields
Class 12 · Electric Charges & Fields
Electric Flux Through Surface
Φ = E·A·cosθ. Tilt the loop and watch flux follow a cosine curve.
Key Notes
01
Electric flux Φ = ∫ E⃗·dA⃗ measures the number of field lines crossing a surface.
02
For uniform E: Φ = EA cosθ, where θ is the angle between E⃗ and area normal n̂.
03
Maximum when n̂ ∥ E⃗ (θ=0), zero when perpendicular (θ=90°).
Formulas
Flux
Surface integral; SI unit V·m.
Uniform E
For flat area in uniform field.
Important Points
Flux is a SCALAR with sign — depends on orientation of n̂.
Closed surfaces use outward normal by convention.
Electric Flux Through Surface notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 12 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.