AC Test Flashcards
What are Capacitors?
Devices that oppose a change of voltage
What 3 factors determine the capacitance of a capacitor?
- The surface area of plates
- The distance between plates
- The type of dielectric used
When can current flow in a capacitor?
Only during the period of time the capacitor is charging or discharging
What type of current flows through the dielectric material?
Leakage current(proportional to resistance)
How does a capacitor store energy?
Through an electrostatic field
What is dielectric stress?
The stretching of electron orbit/ atoms of the dielectric
The function of a diode?
Changes the AC voltage back into DC voltage and charges the capacitor
The basic unit of capacitors?
Farad
Capacitors charge and discharge at what rate on a graph?
Exponential rate
Formula for RC time Constants?
T= R X C
True or false: capacitors can be used to determine power factor corrections?
True
What 2 groups are capacitors divided in?
Non-polarized & polarized
True or false: Non-polarized capacitors can only be connected to DC circuits
False
They can be connected to AC & DC
What are polarized capacitors often referred as?
Electrolytic capacitors
True or false: polarized capacitors can only be used in DC circuits
True
What are 2 types of electrolytic capacitors?
Wet and Dry type
Can variable capacitors change their capacitance values?
Yes to certain range
What are variable capacitors rated in?
Picofarads
How can capacitors be marked?
- Written on
- Colour coded
- Number coded
- Letters to indicate capacitance value
3 types of capacitors
- Ceramic capacitor
- Dipped tantalum capacitor
- Film capacitors
What does a micro-ammeter indicate?
Any current flow between the plates of the dielectric
How many time constants are required to charge or discharge a capacitor?
5
