Why does the current increase and then drop slowly during this capacitor  demo ?

Capacitors | 2 | 3 |
Advanced Capacitance   


 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


apacitors 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  


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.



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)


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
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!
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 >>>>