EF: Electric Field
Introductory Physics

Micro-model of Charge, Q-transfer, Conductors vs. Insulators

Electric Forces and Coulomb's Law

Combined Coulomb’s (electric forces) and Newton’s second laws practice problem

Two ping pong balls filled with air are tied to a very light 0.5 meters-long string. The loose ends of the strings are taped to the same position on a horizontal ceiling. When both are equally rubbed with the same material, they develop a static charge and repel each other, making an angle of 30° with respect to the vertical. (m = 3 grams) 

(A) With this experiment alone, can you tell what type of charge is on the balloon? Explain. 

(B) Is this a stable or unstable equilibrium? 

(C) Estimate the number of excess charges on each balloon. Clearly state any assumptions made in your estimation. 

Field Model, Charges in an Electric Field

Electric Field from Point Charges

Electric Fields Patterns

Notes and More Practice Problems 

Electric field and electric potential