# Flux

Learning objectives

• Develop an intuitive understanding of flux through a surface
• Distinguish between a flux and a flux density
• Motivating example is mass flux:  $\int_S \vec F \cdot d\vec A$ where
• $S$ is an oriented surface in 3-space
• $\vec{F}$ is a vector field in 3-space, units $\hbox{kg}/(\hbox{meter}^2 \cdot \hbox{second})$
• Compute flux integrals geometrically
• when vector field is tangent to the surface
• when vector field is orthogonal to the surface and of constant magnitude on the surface
• Compute some flux integrals analytically using surface parameterizations

Before class

• Read Hughes-Hallett section 19.1, 19.2
• Ponder Hughes-Hallett problems:  19.1: 1, 2, 10, 11, 37, 38; 19.2: 5, 13, 21.

In class