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Gauss’ Law. The density of field lines is related to the magnitude of the field. The amount of field passing through a surface is the flux . Flux. A closed surface is an area that completely surrounds some volume. Sphere or box The flux can be measured through the closed surface.
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The density of field lines is related to the magnitude of the field. The amount of field passing through a surface is the flux. Flux
A closed surface is an area that completely surrounds some volume. Sphere or box The flux can be measured through the closed surface. Closed Surface
The field from a point charge is radial outward. The magnitude drops as r2. A sphere that surrounds a point charge at its center will have filed lines perpendicular. The area increases as r2. The flux is independent of the radius of the sphere. Point and Sphere
Gauss’ Law • The relationship between the flux and the enclosed charge is Gauss’ law. • Flux measures the total charge • Independent of shape • Gauss’ law is often easier than calculating Coulomb’s law for a large number of charges.
A long wire of length L has a uniform positive charge Q. use Gauss’ law to find the electric field at a perpendicular distance r from the midpoint of the wire. Use a closed cylinder for the surface. The field must be radial from the wire. No flux through the ends All field lines perpendicular to curved surface. Apply Gauss’ law: Charged Wire
