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Aluminum Electrolytic Capacitor
A capacitor made up of two aluminum electrodes seperated by paper saturated with an electrolyte. The dielectric is the oxide of the anode.
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Anode
The positive electrode of a capacitor.
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Blocking
A situation where Direct Current (DC) is kept from a circuit element due to the high series impedence of a capacitor.
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By-passing (De-Coupling)
A situation where the AC portion of a signal is kept from a circuit element via a low impedence path in parallel with the circuit element.
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Capacitance
A measure of the energy storage capability of a capacitor at a given voltage usually expressed in farads, microfarads, nanofarads, or picofarads.
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Capacitive Reactance (Xc)
The opposition to the flow of alternating or pulsating current by a capacitor measured in ohms. The imaginery component of the impedence of a capacitor.
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Capacitor
A passive circuit element capable of storing electrical energy and releasing it at a predetermined time and at a predetermined rate.
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Cathode
The negative electrode of a capacitor.
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Charge
The quantity of electrical charge measured in coulombs.
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Coupling
Situation where two circuits are connected together where only the AC voltage is passed.
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Current
The amount of charge moving past a given reference point over time.
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Dielectric
An insulating or non-conductive medium between the plates of a capacitor.
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Dielectric Absorption
A measure of the reluctance of a capacitor's dielectric to discharge completely - usually measured in percent of original charge.
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Dielectric Constant
The ratio of a capacitor's capacitance with a given dielectric to the same capacitor having a vacuum as a dielectric.
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Dissipation Factor (D.F. or Tan delta)
A measure of the losses in a capacitor expressed as the ratio of the E.S.R. of a capacitor to its reactance at a specific frequency and temperature.
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dv/dt Rating
The maximum voltage rise (or discharge) time a capacitor can withstand being damaged.
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Electrolyte
A current-conducting solution between the electrodes of a capacitor used to replenish the dielectric in an aluminum electrolytic capacitor.
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Equivalent Series Resistance (E.S.R.)
The sum of all the internal resistances of a capacitor measured in ohms. Expressed mathematically as ESR = D.F.*Xc.
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Farad
The basic unit of a measure of a capacitor. A capacitor charged to 1 volt with a charge of 1 coulomb would have a capacitance of 1 farad. 1 microF = .000001 Farads.
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Frequency
The rate at which an alternating or pulsating wave repeats itself expressed in cycles per second (C.P.S.) or hertz (Hz).
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Impedance (Zc)
The total opposition offered to alternating or pulsating current measured in ohms. Impedence is the vector sum of the resistive and reactive components of a capacitor expressed mathematically as
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Insulation resistance
The ratio of the DC voltage applied to the terminals of a capacitor and the resultant leakage current flowing through the dielectric and over its surface after the initial charging current has ceased expressed in megohms or as time constant megohm x microfarads.
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Leakage Current
Measure of the stray direct current flowing through capacitor after DC voltage is impressed on it.
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Metallized Capacitor
A capacitor where a thin layer of metal is vacuum-deposited directly onto the dielectric.
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Ripple Current
The total amount of alternating and direct current that can be applied to a capacitor under specific conditions without causing a failure.
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