Capacitors
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Advanced
Capacitance
CAPACITORS CAN STORE A LETHAL
CHARGE
always discharge a capacitor with one hand holding an insulated
screwdriver
the other hand behind your back!!
bleeder resistors that normally drain the capacitor
be defective .... the capacitor will remain charged to
line votage
Capacitors
are electrical components that can store and then release electrical
charge that is stored in an electrostatic energy field.
Stud welders in automated manufacturing processes often use the energy
stored in capacitors to melt steel.
> the energy released from large
capacitors
can be powerful enough to power a spot welder or accelerate a hybrid
vehicle
> capacitors can be used to
create phase shifts
in inductive circuits AC or to
start rotation of split phase motors
> in power supplies capacitors are used to
filter
(remove certain frequencies)
power and communications circuits
> the predictable times taken to
charge
and discharge
capacitors make them useful for
timing circuits and oscillators
Construction
All capacitors have the same basic construction:
2 plates
separated by an insulating material called a
dielectric material
- plates are often made of foil that is wrapped around a sheet of
dielectric material
(I once built the tuner for my first
radio from chewing gum wrapper)
- sometimes the dielectric material is
air, paper, oil, tantalum, electrolyte, or other material depending on the
need
Action > Capacitors store electrical energy as an electrostatic field between the 2 plates when charge is moved from one plate to the other by a difference in voltage.
...........................
Units
Capacitors are rated by how much electrical
charge they can store
per volt applied.
Thus
C =
Q/V
where Q = Coulombs
(6.24 x 1018 electrons)
C = FARADS = Q/V
Think
of a balloon. The greater the
pressure the more air
it contains.
The first few breathes of air are easy the last ones are hard. Air rushes
out of balloon quickly at first. Then slowly later. Apply too much air
pressure to a balloon and it pops.
Substitute voltage for
pressure and electron charge for air and you have capacitor action.
Typically
Capacitors are rated as
>
micro Farads
uF
10-6 Farads
>
pico Farads
pF 10-12
Farads or 1 trillionth Farad
1000,000 picoFarads = 1 uF
1,000,000 uF = 1 Farad
small disc capacitors for high frequency timing and
filtering
(usually no polarity
observed)
= 1 microfarad = uF =
10-6 Farads
= 1 millionth
typical
electrolytic capacitor used everywhere in electronics
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
(observe polarity band on
negative)
- 1 millifarad (mF) = one thousandth (10−3) of a farad or 1000 μF
- 1 microfarad (μF, or MFD in industrial use) = one millionth (10−6) of a farad, or 1000000 pF, or 1000 nF
- 1 nanofarad (nF) = one billionth (10−9) of a farad, or 1000 pF
- 1 picofarad (pF) = one trillionth (10−12) of a farad
1 million microfarads = 1 F
(Farad)
Car audio capacitor used to deliver pulses
of extended bass audio signal to high power speakers during the down beat.
Ever see a car audio system dim the headlights to the bass beat of the
tune. That system needs larger capacitors on the input that can supply
instantaneous
pulses of energy to the amplifier.
The capacitor must charge quickly between
beats and so must have a short Time Constant
Capacitors are rated by the charge
they can store per volt (Farads) AND maximum voltage.
A capacitor that is connected to a voltage that is to high will EXPLODE
with a bang. They can
cause harm!
Can
shaped
electrolytic capacitors must be installed with correct polarity or they
can explode!!! Look
for the band (negative electrode).
Tiny trimmer (variable) capacitor used to
fine tune an oscillator or timer circuit
Variable air capacitor used to tune in
radio frequencies
High voltage industrial oil dielectric
capacitor
eestor hypercapacitors
Maxwell Ultracapacitors
Ultracaps in Hybrid Cars
RickRoll Capacitor
Capacitor charge discharge times
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