Parallel plate capacitor Flashcards
Define capacitance
The charge stored by a capacitor per unit potential difference
State the equation for capacitance
C = Q/V
What is a capacitor?
An electrical component which stores charge
What is a capacitor made up of?
Two conducting parallel plates with a gap between them separated by an insulating material (dielectric)
What happens when a capacitor is connected to a power source?
Opposite charges build up on the two parallel plates causing a uniform electric field to be formed
Define permittivity
A measure of the ability to store an electric field in a material
A measure of how difficult it is for charge to pass through a material
How do you work out relative permittivity?
(dielectric constant of a dielectric)
Permittivity of dielectric / permittivity of free space
State the equation for capacitance
C = Ae0er/ d
What is a dielectric made up of?
Polar molecules where one end is positive and the other negative
When there is no electric field how are molecules in a dielectric arranged?
In random directions
When there is an electric field how are molecules in a dielectric arranged?
They move and align themselves with the field. The negative ends are rotated towards the positive plate and the positive ends towards the negative plate
What value depends on the dielectric’s permittivity?
The electric field strength of each molecule
State the equation for the energy stored by a capacitor
E = 1/2 x QV
State alternative equations for the energy storied by a capacitor
E =1/2 x CV2
E = 1/2 x Q2/C
How does the potential difference required to charge the capacitor decreases?
The electric fields of the molecules oppose the field formed by the capacitor, reducing the field
(Causes capacitance to increase)
