Capacitance Flashcards
Capacitor Definition
A pair of conducting plates separated by an insulator, if a potential difference is placed across the plates they acquire equal and opposite charges.
What is Capacitance measured in?
Farads, F
Dielectric Definition
Insulator between the plates of a capacitor, also serving to make the capacitance larger than if there were just empty space
What is given by the area under a Q-V graph
Energy stored by the capacitor
The energy stored within the capacitor is given by the symbol U, since …
the energy is stored inside the capacitor (as electrostatic potential energy) and hence is classed as internal energy
State one assumption made about electric fields between the plates of a parallel capacitor
it is assumed to be uniform, so hence the electric field strength will have a constant value
Capacitance Equation(hint: Both)
C = Q/V
or
C = ℰA/d
Three Equations for energy stored by a capacitor
U = 1/2QV
and U = 1/2CV^2
and U = 1/2Q^2/C
Electric Field Strength Equation
E = V/d
or
F/Q
What is the equation for combining capacitors in Series
1/Ct = 1/C1 = 1/C2
What is the equation for combining capacitors in parallel
Ct = C1 + C2
Does the Equation for Charging capacitors for charge involve subtracting anything from 1
Yes
Does the Equation for discharging capacitors for voltage involve subtracting anything from 1
No
What is the equation for current when discharging the capacitors
Q = It
