Capacitance and Capacitive Reactance Flashcards
What is a capacitor?
Two metallic plates, separated by a dielectric material.
What is the insulating material between a capacitor’s plates called?
the dielectric.
There are six types of non-polarized capacitors, what are they? What is their primary useful function.
Air (capacitance can be easily varied),
Oil- filled (usable in power circuits with high I and V),
Paper (large capacitance in a small package),
Plastic film (like paper, but utilize a different dielectric),
Mica (high capacitance, with a strong dielectric),
Ceramic (high capacitance for their small size).
When a symbol for a core is drawn with two parallel lines next to it, whet is signified by this addition?
The core is a magnetic material like iron.
What factors will affect capacitance?
The area of the plates,
distance between the plates,
and the type of dielectric.
The symbol for capacitance is ______, it is measured in ______.
C,
Farads (F), typically microfarads.
What is capacitance?
The property of a circuit to oppose a change in voltage.
It may also be defined as the ability to store electric charge.
What are the two basic ratings of a dielectric?
Dielectric strength: voltage insulating strength,
Dielectric constant: material’s ability to polarize and store charge, compared to air.
When connecting a capacitor rated in WVDC into an AC circuit, what must be observed.
The peak AC voltage must not exceed the WVDC rating.
Which capacitors may be only used in DC, how can they be modified to be used in an AC circuit?
Polarized electrolytic.
By connecting two of the same polarity plates in a back to back series arrangement, it is certain that in an AC circuit one side always has the correct polarity.
What are some common capacitor applications?
Timing,
Rectifier smoothing and filtering,
Power factor correction,
and Single phase motor starting.
How could one calculate the charge held by a capacitor?
Multiply the measured capacitor voltage by it’s capacitance.
When a capacitor is placed in a DC circuit, how will the voltage across the capacitor rise to it’s maximum value as the circuit is closed?
The voltage across the capacitor will rise quickly at first and slow down gradually. It may never reach 100% of it’s steady value.
How can we define the time it takes for capacitor voltage to reach it’s steady value?
We can define it as five time constants, which are defined as the product of capacitance and resistance.
How much will the capacitor voltage change in each time constant?
Voltage will increase by 63.2% of the remaining value to reach it's maximum, after every time constant. Tc1 = 63.2% Tc2 = 86.4% Tc3 = 95% Tc4 = 98.1% Tc5 = 99.4%, Which is essentially 100.
