Download Chapter 24

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
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?
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?
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?
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?
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?
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?
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?
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?
the end