Chapter 25 Concepts - Capacitance Flashcards
What is a capacitor?
A device in which electrical energy can be stored.
What is capacitance (C)?
The amount of charge that can be stored in a capacitor.
What does capacitance depend on?
The geometry of the plates and not on their charge or potential difference.
What are the basic units for capacitance?
1 Farad (F) = 1 Coulomb/Volt
What are the steps to finding geometric capacitance?
1) Assume a charge q on the plates
2) Calculate the electric field between the plates in terms of this assumed charge
3) Calculate the potential difference between the plates
What does PAR-V mean?
Parallel capacitors have the same potential difference
What does SERI-Q mean?
Series capacitors have the same charge
What is energy density (u)?
The potential energy per unit of volume
What is a dielectric?
insulating material
How do dielectrics affect capacitance?
Capacitance increases when there is a dielectric present between the plates by a factor of the dielectric constant.
What happens when the maximum potential difference is exceeded?
The dielectric material will break down and form a conducting path between the plates
How do dielectrics affect the electric field?
Weakens the electric field
Define dielectric strength
the maximum value of the electric field that it can tolerate without breaking down
Define polar dielectrics and their relevance to an electric field.
molecules of dielectrics that have permanent electric dipole moments.
The alignment of the dipoles produces an electric field that is directed opposite the applied field and is smaller in magnitude.
Define nonpolar dielectrics.
molecules acquire dipole moments by induction when placed in an external electric field
