Jun Ming Liu: The Capacitor

The capacitor stores electric charge and also can discharge it. There are two metal plates close together and separated by an insulator. Those two plates one is positive and the other is negative. Non-electrolytic capacitor is no polarity requirements. The charge stored depends on the size or capacitance of the capacitor, and its unit is Farads.

Identify the capacitor

This is Non-electrolytic capacitor, no polarity requirements, it can take high voltage.

This is electrolytic capacitor . The terminal which is marked "-" is negative. The polarity must be corrected in circuit. It has leakage current.

This is tantalum capacitor. It is physically smaller and lower leakage.

This is variable capacitor, it can adjust the capacitance.

EIA code

EIa code is shown the capacitance of the capacitor. It consists 3 numbers. To identify the capacitance, write down first 2 numbers, then add numbers of zero as the third number shown.
i.e: EIA code is 105. the capacitance is 5 zero after 10, it is 1,000,000F

Charge Time
Capacitors take time to charge, to calcualte the time, the formula is T=RxCx5. R is the resistance in the circuit, C is the capacitance of the capacitor.
Capacitor charged 2/3 applied voltage in first 1/5 time of charging, then the speed of charging slow down.

Exercise
Build the circuit show as below, calculate and observe the charge time of the capacitor.

Calculation:
1. C=100uF R=1Kohm
   Calculation: T=5xRxC= 5 x 1000ohm x 100 x10(-6)F = 500mS

2. C=100uF R=0.1Kohm
   Calculation: T=5xRxC= 5 x 100ohm x 100 x 10(-6)F = 50mS

3. C=100uF R=0.47Kohm
   Calculation: T=5xRxC= 5 x 470ohm x 100 x 10(-6)F = 235mS

4. C=330uF R= 1Kohm
   Calculation: T=5xRxC= 5 x 1000ohm x 330 x 10(-6)F = 1650mS

Observation:
Bulit the circuit on breadboad: