1. Example: A negatively charged rod, of length l, has a total charge Q and is a distance b from a point P. The charge is uniformly distributed along the length of the rod. • What is the net electric field at point P? • What is the net force on a negative charge q placed at point P? a) F E Down b) Up

2. Motion of charged particles in an electric field • An electric force will cause charged particles to accelerate (similar to how a mechanical force causes objects to accelerate). • A constant force will cause a constant acceleration, therefore we can use the same kinematic equations that were developed in the beginning of the previous semester of this course. Note: The force does not have to be constant!

3. Application: CRT (Cathode Ray Tube) • A beam of electrons is fired between a pair of parallel charged plates. • There is an electric field directed from the positive plate towards the negative plate. • The electric field will deflect the electrons towards the positive plate. • The strength of the electric field determines the amount of deflection that occurs. Note: These diagrams contain more complex CRT devices which also incorporate magnetic interactions.

4. The electric field generated by a positive point charge travels away from the point charge and passes through a region of space. • It is sometimes necessary to discuss the amount of electric field that passes through a certain region of space. • This is called Electric Flux. Cross-sectional area of rectangular volume of space E and A are parallel FE – Electric Flux E – Electric Field Strength A – Cross-sectional Area [m2] Effective cross-sectional area of rectangular volume of space at an angle relative the direction of the electric field E and A are not parallel Acosq is the effective area