Capacitance

• The ability to store an electrical current
  
  

Capacitor Charging /Discharging

• When a DC voltage is applied to a capacitor, the capacitor begins to charge

• The charging continues until the potential difference across the capacitor is equal to the applied voltage

• Once charged there would be no further current flow until the polarity is reversed

• When an AC voltage is applied to a capacitor, the capacitor begins to charge during the first half cycle to peak the capacitor will discharge
  and try to keep the voltage at the level of peak. During the second half cycle this process repeats but in the reversed polarity
  
  

• Capacitance – The property of a circuit, which opposes and change in the circuit voltage
  
  

• Capacitor – An electrical device used to supply capacitance in a circuit
  
  

• Capacitor Charge – The flow of electrons onto one plate and away from the other, resulting in a negative charge on one plate and positive charge on the other
  
  

• Capacitor Discharge – The flow of electrons from the negative charged plate of a capacitor to the positively charged plate, eliminating the charges on the plate
  
  

• Farad – The basic unit of capacitance where 1 coulomb of charge for 1 second yields a potential difference of 1 volt

• Potential Units of Capacitance – The basic units are microfarad (one-millionth farad) and picofarad (one-millionth – millionth of a farad)
  
  
  

Capacitance Opposes Any Charge in Circuit Voltage

• When the voltage increases capacitance tries to hold it down

• When the voltage decreases capacitance tries to hold it up

Capacitive Reactance:

• Opposition to current flow in a capacitive circuit
  
  

Capacitor Construction:

• 2 conducting plates separated by any insulating material called a dielectric
  
  

Factors that Affecting Capacitance:

• Distance between plates (plates closer = increased capacitance)
• Dielectric Material (properties of the material affects the capacitance)
• The area of the plates (larger plates = increased capacitance)

ICE (current in capacitive circuit leads voltage by 90 degrees)

Example:

• To remember whether current leads or lags voltage in a capacitor or inductor, remember the phrase 
  
  “ELI the ICEman”
• "ELI" reminds you that the voltage (E) in an inductor (L) leads the current (I), and "ICE" reminds you that the current (I) in a capacitor (C) leads the voltage (E).