Capacitance Flashcards
How is the charge stored on a capacitor related to the capacitance of the capacitor and the potential difference across the capacitor?
The charge equals the product of the capacitance and the potential difference
When a battery charges a capacitor, what happens to the conduction electrons?
electrons leave the plate that becomes the positively charged; electrons enter the plate that becomes negatively charged
Which do we do to find the equivalent of capacitors in series?
We sum the inverse of each capacitance and then invert the sum
What is true about capacitors in parallel?
They have the same potential difference
Which is true about the equivalent of capacitors in parallel?
The equivalent capacitance is more than the largest value of the individual capacitances
Which is true about the equivalent of capacitors in series?
The equivalent capacitances is less than the smallest value of the individual capacitances
If we were to gradually charge a capacitor by transferring charge from one plate to the other, which describes the work per unit charge required of us?
It gradually increases from start to end.
If we were to gradually charge a capacitor by transferring charge from one plate to the other, which describes the action of the electric field between the plates?
It resists our transfer of charge.
How does the amount of energy stored in a capacitor depend on the capacitance?
It is proportional to the capacitance.
What happens to the amount of energy stored in a capacitor as we increase the potential difference between the plates?
It increases.
Capacitance depends on only geometry of capacitor
shape and size of plates, and their separation distance.
A battery transfers electrons from one plate to the other until the capacitor is fully charged. When the capacitor is fully charged,
the plates produce the potential difference that equals the potential difference between terminals of the battery
A battery maintains
potential difference between its terminal
Equivalent capacitor
a single capacitor that has the same capacitance as a network of capacitors in a circuit
Capacitors in parallel:
Capacitors are directly wired together at one plate and directly wired together at the other plate
- same potential across each capacitor
Capacitors in series:
Capacitors are wired serially, one after the other. Charge stored on each capacitor is the same.
- q is the same for each capacitor
In series, two networks are equivalent if
they have the same junction structure
- same # of junctions
- 2 circuits split into the same set of capacitors at each junction
The energy stored in the capacitor is
equal to the work done to charge the capacitor
If capacitors are connected in parallel
the capacitor with the greatest capacitance stores the greatest amount of energy
If capacitors are connected in series
the capacitor with the smallest capacitance stores the greatest amount of energy.
Where does a capacitor store its energy?
In the electric field
Dielectric breakdown
Any insulating material permits electric conduction if it is subjected to a sufficiently strong electric field.
How do we increase capacitance?
We fill the space between plates with an insulating material
Capacitance depends on
the dielectric material between the plates and geometry of capacitor
Dipole moments of a dielectric
decrease the strength of the electric field by producing an electric field opposes the applied electric field.
polar dielectric
molecules have permanent dipoles that align with the applied field
non-polar dielectric
dipole moments are induced by the applied field
