Introduction to Capacitors

                Introduction to Capacitors

• A capacitor is a passive electronic component used to store electric charge. 
• The unit for measuring capacitance is Farads. 
• The standard capacitor values are 1, 10,100,510,910pF 
• Capacitors are also marked with color bands to denote value. 
• The first 2 bands are the first and second digit whereas the third band denotes the multiplier. 
• Symbol for capacitor is shown.
  
• Capacitor tolerance is the value which determines the extent to which capacitance can vary from actual capacitance. 
• It ranges from ­20% to +80% 

• Temperature Co­efficient 

1. The temperature co efficient is the maximum change in a capacitance with change in temperature. 
2. It is measured in ppm/◦C (Parts per million by degree Celsius)

• The factors affecting capacitor behavior are as follows:

Breakdown voltage, Equivalent circuit, Q factor, Ripple current, Instability, Dielectric absorption, Leakage, Current and Voltage Reversal

1. Breakdown voltage: The voltage at which the dielectric capacitor becomes conductive is called breakdown voltage. 
2. Equivalent circuit: All capacitors also have some resistance called Equivalent series resistance which adds up to the impedance. 
3. Q factor: It is used to measure efficiency and is the ration of its reactance to its resistance. 
4. Ripple current: Ripple current is the component of AC which generates heat in the capacitor. 
5. Instability: As the capacitors begin to age, capacitance of certain capacitors decreases. 
6. Dielectric absorption: Capacitors containing dielectric material show dielectric absorption which generates voltage. 
7. Leakage: Constant exposure to heat causes leakage in dielectric. 
8. Current and Voltage Reversal: Current reversal occurs when current changes direction and voltage reversal occurs when there is change in polarity and these reversals cause excessive heating in capacitor.