Capacitors Flashcards
Define capacitance
Amount of charge an object is able to store per unjt potential difference across it
What is a capacitor?
-Electrical component that can store electric charge
-made up of two electrical conducting plates separated by an electrical insulator
Circuit symbol:
How do capacitors work?
(When connected to a direct current) charge builds up the plates, each plate becoming oppositely charged
-electrical insulator inhibits charge moving across
Finding capacitance given a Q V of V Q graph
Area underneath
Definition of permittivity
A measure of how difficult it is to generate an electric field in a medium
-higher permittivity means greater current required to produce same size field
Equation for relative permittivity of a material
What is another name for relative permittivity?
Dielectric constant
How do polar molecules in a dielectric behave once an electric field is present?
-Initially molecules are aligned randomly
-Once field is applied, negative ends of molecules face Positively charged plate and positive elements of molecules face negatively charged plate
Label the values in this equation
Graphs of I, V and Q against time for charging a capacitor (with fixed resistor)
Graphs for I, V and Q for discharging a capacitor (fixed resistor)
Equations of voltage and current variation for capacitor charging
Equations of Q, V and I variation for capacitor discharging
Time constant
T=rc
Time taken for charge on a discharging capacitor to fall to 37% of original value (vice versa with charging, only with 63%
Time to halve (for Q, V or I)
