184_notes:patterns_fields [Projects & Practices in Physics]

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
/*[[184_notes:motiv_movingq|Next Page: Modeling Moving Charges]]

[[184_notes:dist_charges|Previous Page: Distributions of Charges]]*/

===== Patterns in the Electric Field =====
In the last page of notes, we talked about two different examples of distributions of charges (both spheres and cylinders) for both conducting materials and insulating materials. It is worth highlighting some common features and patterns of fields for these larger shapes.

====Direction of Electric Field====
  * Electric field should point radially away (for a positive charge) or toward (for a negative charge) a sphere 
  * Electric field should point radially away (for a positive charge) or toward (for a negative charge) a cylinder - //except near the ends// 

====Magnitude of Electric Field====
  * If you are looking for the electric field **outside** the object with a simple shape (sphere, cylinder), **it doesn't matter if it is an insulator or conductor - the electric field will be the same (for the same amount of charge uniformly distributed).**
  * If you are looking for the electric field inside a conductor, it will always be zero (no matter what the shape).
  * If you are looking for the electric field inside an insulator, it will likely be non-zero (expect perhaps in the very center for certain cases).

====Where charges are located====
  * Charges move to the surface of conductors - there is not net charge inside the conductor (the atoms are still there, but they are neutral).
  * Charges stay where they are placed on insulators - it is possible to have net charge in inside an insulator.

====Approximations====
  * If you are looking for the field outside of a sphere with a uniform distribution of charge, we will often approximate the //sphere as a point charge// because the electric field is the same for both of these cases.
  * If you are looking for the field outside of a cylinder with a uniform distribution of charge, we will often to approximate the //cylinder as a line of charge// because the electric field is the same for both of these cases.