CHAPTER 7: ELECTROSTATICS II

Electrostatics is the study of electric charges at rest. This chapter moves beyond simple charges to explore the electric fields they create and the devices—capacitors—that store electrical energy using these fields. From the simplest parallel plate capacitor to the complex circuits in your phone, these principles are everywhere.

7.1 ELECTRIC FIELDS

An electric field is a region of space around a charged object where another charged object experiences an electric force. The field is a vector field—it has both magnitude and direction at every point.

7.1.1 Representing Electric Fields: Field Lines

Electric fields are visualized using electric field lines (also called lines of force). The rules for drawing these lines are:

• Field lines start on positive charges and end on negative charges.
• The direction of the field at any point is tangent to the field line at that point.
• The direction indicates the force on a positive test charge placed at that point.
• The density of field lines indicates the strength of the field (closer lines = stronger field).
• Field lines never cross.

7.1.2 Field Patterns for Point Charges

7.1.2.1 Isolated Positive Point Charge

• Direction: Radially outward (away