Applications:	Function	Notes
Motor starting	The capacitor creates a phase displacement between two winding in order to achieve rotation.	In order too get an armature (rotor) to rotate we need a force to pull the armature in order to start turning so  induction can take place. Since a capacitor causes a phase displacement between the voltage and the current for an AC supply, it does the job perfectly. Soon as the armature rotates the motor is happy and we can cut this additional winding + capacitor out of the circuit. Now lets share a bit ofd criticalnformation here to prevent any blow ups: The capacitor is measured in micro-Farads. Each motor design requires it exact amount of capacitance to do the starting...so it is best to replace with equal. I don't say another value might not work...for we all know what happens in the workshop...what I am saying by design we come to an exact value and is is best to stick with this value. Motor starting capacitors are high voltage for a reason and that 400/450V volts rating is there to accommodate the peak values in the AC supply.  And this brings us to the last point: A motor starting caps is a electrolytic type cap but the "normal electrolytic caps are polarised meaning it cannot be used in AC supply. They look the same and sometimes even have the same voltage rating but if it has the +(positive) and the ---(neg) on the casing - that's a animal for a different job. Don't even try to use them -these caps explode with a bang and it flies all over the show. There my say is said, hopefully it helps. See if you can spot  the difference: ---
Power factor correction	The effect of inductance on a AC supplied circuit is to create a phase displacement between the voltage and the current. By how much the current will then lag the voltage is a function of how much inductance is in the circuit. The effect of capacitance in AC supplied circuit is that the voltage lags the current by as much capacitance is in the circuit. This is the direct opposite to the effects of inductance. This means we can use one to cancel the other...and this is exactly what power factor correction is all about, bringing that voltage and current back in phase because if they are not we don't have efficient power usage. But be careful because if they are exactly / totally equal a phenomenon called resonance happens and then things become very unpredictable. Then we have to add reactors (chokes - yes more inductance!) but they are said to be detuned.

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Capacitor values and markings:

Unit
Farad	1F	10Exp-0	1 Farad
Micro- Farad	1uF	10exp-6	0.000001 Farad
Nano – Farad	1nF	10Exp-9	0.000000001 Farad
Pico – Farad	1pF	10exp-12	0.000000000001 Farad

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Similar to resistors - in electronics capacitors also have markings where each colour signifies a specific piece of information:

In reality, for capacitors the colour markings is not so easy as with resistors...you get the funniest ways manufacturers can mark the caps. What I do is make sure I mark them when I receive them...that way there is no crisis.

My rhyme to remember the colours goes like this:

Black BROY Gave BeV a Grey Whip