1. Lecture 21 For a long wire with current I, we have found at P, a distance r from the wire: B has a curly field pattern, it is into the page at P and out of the page at P’. Top View: (1) circle

2. Ampere’s law takes the form: Denote: Where S is the Amperian Loop an I is the current through the loop. More specifically

3. Long, thick wire: Assume current density is uniform. Notations:

4. Coaxial Cable (example problem):

5. Discussion on example problem

6. (out) (into) Find: B at P

7. Solenoid Discussion