# Lect_33 - Flux in General DEMO Loop Lecture 33 Electric...

This preview shows pages 1–3. Sign up to view the full content.

Lecture 33 Electric Flux Gauss’s Law Flux in General Flux in General Max. flux Flux = 0 Less flux Flux: How much of something is passing through a surface. Flux depends on: The flow of the water The area of the tennis racquet A . How many hairs are passing through your scalp. If you dip a tennis racquet in a river, how much water flows through it? The orientation ( θ ) Effective area AA cos 0 DEMO: Loop Area vector A θ Is a vector with: Magnitude: Area of surface Direction: Perpendicular to surface Electric Flux Φ Φ =⋅ G G Eda In general (for any field and surface): Instead of water, we have electric field lines. How many lines go through a given surface? For uniform E and flat surfaces only 2 [] Nm/ C Vm Φ= = effective EA Φ = Line density is proportional to the magnitude of the electric field: cos = = G G

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ACT: Flux through open surface ACT: Flux through open surface Two rectangles with one identical side (perpendicular to the screen in the side view) and one different side are placed in a region with a uniform electric field E. The areas of the rectangles are A 1 and 2 ( 2 > 1 ). 2 1 (Side view) E (Front view of rectangles) 1 2 Compare the electric flux through the two rectangles: A. Φ 1 < Φ 2 B. Φ 1 = Φ 2 C. Φ 1 > Φ 2 2 1 (Side view) The number of lines going through them is the same. 2 θ 2 cos The effective area for the large square is 2 cos = 1 Sign matters! If you reverse the direction of A, you reverse the sign of the flux • For an open surface, choose any direction as long as the choice is made clear •For ±a ± closed surface , the convention is to take the area vector pointing outwards Flux > 0 lines going out Flux < 0 lines coming in Flux = 0 no lines or a balance between incoming and outgoing lines.
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 04/16/2008 for the course PHYSICS 221 taught by Professor Johnson during the Fall '06 term at Iowa State.

### Page1 / 7

Lect_33 - Flux in General DEMO Loop Lecture 33 Electric...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online