16-7 The Electric Field

1. 16-7 The Electric Field • The idea that forces act over a distance and don’t have to be in contact was hard to understand • Michael Faraday developed the idea of a Field • The electric field extends outward from every charge

2. If there is a second electric field placed near the first it feels the force of the first field • The electric field at a point, P, has to consider both electric fields • To do this consider a small positive test charge and determine how the electric fields effect the test charge

3. The electric field, E is defined in terms of the force, F exerted on a tiny positive test charge, +q Units of N/C

4. The electric field at any point in space can be measured

5. 16-8 Field Lines • The electric field is a vector, it is sometimes referred to as a vector field • The electric field line or lines of force indicate the direction of the electric field at various points in space • They are drawn indicating the direction of a force due to the given field on a positive test charge

6. The number of lines starting on a positive charge or ending on a negative charge is proportional to the magnitude of the charge • 1. Electric field lines indicate the direction of the electric field • 2. The number of lines is proportional to the magnitude of the field • 3. The electric field lines start on a positive charge and end on a negative charge • The lines never cross, why not?

7. 16-9 Electric Fields & Conductors • The electric field inside a conductor is zero • The net charge on a conductor distributes itself on the surface • The electric field is always perpendicular to the surface outside of a conductor