Chapter 11 Capacitance

Objectives After completing this chapter, you will be able to: Explain the principles of capacitance Identify the basic units of capacitance Identify different types of capacitors Determine total capacitance in series and parallel circuits Explain RC time constants and how they relate to capacitance

Capacitance Capacitance Capacitor Ability to store electrical energy in an electrostatic field Basic unit is the farad (F) Represented by letter C Capacitor Possesses a specific amount of capacitance Either fixed or variable

Capacitance (cont’d.) Figure 11-1. A capacitor consists of two plates (conductors) separated by a dielectric (insulator or nonconductor).

Capacitors Factors that affect capacitance Area of the plate Distance between the plates Type of dielectric material Temperature

Figure 11-3. Electrolytic capacitors.

Capacitors (cont’d.) Figure 11-4. Paper and plastic capacitors.

Capacitors (cont’d.) Figure 11-5. Ceramic disk capacitors.

Capacitors (cont’d.) Figure 11-6. Variable capacitors.

Capacitors (cont’d.) Total capacitance in series circuits: Total capacitance in parallel circuits:

RC Time Constants Figure 11-7. Circuit used to determine RC time constant.

RC Time Constants (cont’d.) RC circuit time constant formula: t = RC where: t = time in seconds R = resistance in ohms C = capacitance in farads

RC Time Constants (cont’d.) Figure 11-8. Chart of time constants required to charge and discharge a capacitor.

Summary Capacitance (C) allows for the storage of energy in an electrostatic field The unit of capacitance is the farad (F) Capacitor types include: electrolytic, paper, plastic, ceramic, and variable Total capacitance in series circuits:

Summary (cont’d.) Total capacitance in parallel circuits: RC circuit time constant formula: t = RC It takes five constants to fully charge and discharge a capacitor