Table of Contents

# Current

## Prerequisites

**Flux**(for measuring total current)**Charge Density**(for comparison with current density, and/or as an quantity that contributes to current density)

- Reading: GVC § Currents

## In-class Content

- Acting Out Current Density (Kinesthetic Activity - 10 min)
**Note:**Curl is needed for 3 different ideas in this class: Conservative Work, Going from $\vec A$ to $\vec B$, and getting from $\vec B$ to $\vec J$. - Current Density (lecture)
*10 min*

## Homework for Static Fields

- (TotalCurrentGEM55)
*Calculate surface current density $K$ and volume current density $J$ for a wire carrying total current $I$, from Griffiths E&M book.*A current $I$ flows down a wire of radius $a$.

If it is uniformly distributed over the surface, give a formula for the surface current density $\Vec K$.

If it is distributed in such a way that the volume current density, $|\Vec J|$, is inversely proportional to the distance from the axis, give a formula for $\Vec J$.

For the surface current you found in Problem 1.a, find the magnetic vector potential at a distance $r$ from the center of the wire with length of $2L$.