capacitors Flashcards
state three places where capacitors are used
- radios
- TV sets
- computers
what do capacitors do
store electrical energy in circuits
what is capacitance measured in
farads, F
why is micro-farads the most common unit of measurement
- 1 farad is quite a large capacitance
- it is unlikely to be dealing with such large capacitances
how many leads does a capacitor have
two
what two things are needed to make a simple capacitor
- metal plates
- two wires
how can large plate areas be achieved with cylindrical capacitors
by rolling them up
formula for capacitance
capacitance = charge / p.d.
C = Q/V
what is capacitance defined as
capacitance is the charge stored per unit potential difference across a capacitor
capacitance in parallel
The total capacitance of two (or more) capacitors in parallel is CParallel = C1 + C2
time constant
- time taken for potential difference to fall 1/e of its original value
t = RC
capacitors in series
The total capacitance of two (or more) capacitors in series
1/Ctotal = 1/C1 + 1/C2
exponential decay
when a physical quantity decreases by the same factor in equal time intervals. e.g., when a quantity halves every 5 seconds
