Presentation on theme: "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."— Presentation transcript:
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. a)What is the net electric field at point P? b)What is the net force on a negative charge q placed at point P? E a) b) Down Up F
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!
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.
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. E – Electric Flux E – Electric Field Strength A – Cross-sectional Area [m 2 ] Cross-sectional area of rectangular volume of space Effective cross-sectional area of rectangular volume of space at an angle relative the direction of the electric field E and A are parallel E and A are not parallel Acos is the effective area