chapter 24 capacitance, dielectrics, energy storage

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Chapter 24 Capacitance, Dielectrics, Energy Storage

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Page 1: Chapter 24 Capacitance, Dielectrics, Energy Storage

Chapter 24

Capacitance, Dielectrics, Energy Storage

Page 2: Chapter 24 Capacitance, Dielectrics, Energy Storage

Introduction: Our approach

• Getting familiar with capacitors

• Defining and calculating capacitance

• Understanding what happens when capacitors are in a circuit

• Understanding energy in a capacitor

• Understanding the role of dielectrics in capacitors

Page 3: Chapter 24 Capacitance, Dielectrics, Energy Storage

Capacitors

• What are the main uses of devices called capacitors?

• How does a capacitor “store charge” without having a net charge?

• How are capacitors constructed?

• In what sense can just about any object be considered a capacitor?

Page 4: Chapter 24 Capacitance, Dielectrics, Energy Storage

Capacitance

• What is the definition of capacitance?

• In general, how can capacitance be calculated from the electric field?

• How is capacitance calculated for a few simple capacitors?

Page 5: Chapter 24 Capacitance, Dielectrics, Energy Storage

Connected Capacitors

• What is meant by a (closed) electrical circuit?

• How are capacitors in circuits represented diagrammatically?

• What is meant by two or more capacitors in series?

• What is meant by two or more capacitors in parallel?

Page 6: Chapter 24 Capacitance, Dielectrics, Energy Storage

Connected Capacitors (cont’d.)

• What is the equivalent capacitance for capacitors in series?

• What is the equivalent capacitance for capacitors in parallel?

• How is the distribution of charge determined when capacitors, some of which were initially charged, are connected in a circuit?

Page 7: Chapter 24 Capacitance, Dielectrics, Energy Storage

Energy in capacitors

• How is the energy in a capacitor defined?

• What is the energy in a capacitor in terms of the capacitance, charge, and voltage of the capacitor?

• How does the energy of a capacitor change as its separation increases? How does it matter whether the capacitor is connected to a battery?

Page 8: Chapter 24 Capacitance, Dielectrics, Energy Storage

Energy in capacitors (cont’d)

• Where is the energy in a capacitor?

• In the above framework, how is the quantity of energy defined and expressed in terms of other quantities?

Page 9: Chapter 24 Capacitance, Dielectrics, Energy Storage

Dielectrics

• What is a dielectric? What are some examples?

• How is the dielectric constant defined?

• Why is it reasonable that a capacitor with a dielectric in the spacing has a greater capacitance?

• What is dielectric strength?

• What is the permittivity of a material?

Page 10: Chapter 24 Capacitance, Dielectrics, Energy Storage

Dielectrics (microscopically)

• What is going on microscopically when a dielectric is in a capacitor?

• What is referred to by E0, Eind, σind, Qind, free charge, bound charge, K?

Page 11: Chapter 24 Capacitance, Dielectrics, Energy Storage

the end