Working Principle of a Capacitor

Definition of Capacitor

Capacitor is a passive electronic component or device capable of storing charge with a certain voltage level across two conducting plates or surfaces, separated by an insulating material or dielectric substance.

Construction of Plate Capacitor

Capacitor is constructed by using two conducting surfaces or plates and an insulating material (i.e. Dielectric like mica, paper, air etc) between these two surfaces.

Working of Capacitor

As a capacitor is passive component, it does not generate energy. But it is able to store energy from an energy source like a battery or another charged capacitor. When a battery (DC Source) is connected across a capacitor, one surface, named plate I gets positive end of the battery and another surface, named plate II gets negative end of the battery. When battery is connected, the full voltage of that battery is applied across that capacitor. At that situation, plate I is in positive potency with respect to the plate II.

Current from the battery tries to flow through this capacitor from its positive plate (plate I) to negative plate (plate II) but cannot flow at max value due to separation of these plates with an insulating material. Rather a very small current will flow through this insulating material (dielectric) from Positive to Negative plate depending upon the value of strength of this dielectric.
An electric field will form inside the capacitor dielectric from positive to negative plate. As time goes on, positive plate (plate I) will accumulate positive charge from the battery and negative plate (plate II) will accumulate negative charge from negative end of the battery. After a certain time, the capacitor holds maximum amount of charge as per its capacitance with respect to this voltage. This time span is called charging time of this capacitor. charging capacitor Now, after removing this battery from this capacitor, these two plates will hold positive and negative charges with respect to a certain voltage level for long time. Thus this capacitor acts as energy source. charged capacitor If two ends (plate I and plate II) get shorted through a load, a current will flow through this load from plate I to plate II up to all charges get vanished from both plates. This time span is known as discharging time of the capacitor. discharged capacitor

How does a Capacitor Respond in DC?

Suppose a capacitor is connected across a battery through a switch. When switch is ON, i.e. t = 0+, a certain value of current will flow through this capacitor. After a certain time (i.e. charging time) capacitor never allow current to flow through it further. It is because of maximum number of charges are accumulated on both surfaces and capacitor acts as a battery which has positive end connected to the positive end of the battery and negative end connected to the negative end of the battery with same potency. Due to zero potential difference between battery and capacitor, no current will flow through it. So, it can be said that, initially a capacitor is short circuited and finally open circuited when it gets connected across a battery.

How does a Capacitor Respond in AC?

Suppose a capacitor is connected across an AC source. Consider, at a certain moment of positive half of this alternating voltage, plate I gets positive polarity and plate II negative polarity. Just at that moment plate I accumulates positive charges and plate II accumulates negative charges. But at the negative half of this applied AC voltage, plate I gets negative charges and plate II positive charges. And so on. There is no flow of electron between these two plates as they change their polarity with the change of source polarity. The capacitor plates get charged and discharged alternatively by the AC.

Types of Capacitor

The types of capacitor are as follows:

Polarized Capacitor

Polarized Capacitors are broadly Classified into following catagories.
Electrolytic Capacitor
Aluminum Electrolytic Capacitor
  1. Non Solid
  2. Hybrid Polymer
  3. Solid Polymer
Tantalum Electrolytic Capacitor
  1. Non Solid
  2. Solid MnO2
  3. Solid Polymer
Niobium Electrolytic Capacitor
  1. Solid MnO2
  2. Solid Polymer
Super Capacitor Double Layer
  1. Class I
  2. Class II
  3. Class III
  4. Class IV
Pseudo Capacitor
  1. Class I
  2. Class II
  3. Class III
  4. Class IV

Non Polarized Capacitor

  1. Metal Insulated Semiconductor Capacitor
  2. Ceramic Capacitor
    • Class I
    • Class II
  3. Film Capacitor
    • Metalized (Paper as Dielectric)
    • Film/Foil (PP Film, PET Film, PEN Film, PPS Film, PTFE Film)


Closely Related Articles Quality Factor of Inductor and CapacitorTransient Behavior of CapacitorCylindrical CapacitorSpherical CapacitorCapacitors in Series and ParallelHow to Test Capacitors?More Related Articles Electric Current and Theory of Electricity | Heating and Magnetic EffectNature of ElectricityDrift Velocity Drift Current and Electron MobilityElectric Current and Voltage Division RuleRMS or Root Mean Square Value of AC SignalElectrical Conductance Conductivity of Metal Semiconductor and Insulator | Band TheoryWhat is Electrical Resistance?Resistivity and Laws of ResistanceProperties of Electric ConductorTemperature Coefficient of ResistanceResistance Variation with TemperatureSeries ResistanceActive and Passive Elements of Electrical CircuitElectrical DC Series and Parallel CircuitOhm's Law | Equation Formula and Limitation of Ohm's LawKirchhoff Current Law and Kirchhoff Voltage LawSingle and Multi Mesh AnalysisSuperposition TheoremThevenin Theorem and Thevenin Equivalent Voltage and ResistanceNorton Theorem | Norton Equivalent Current and ResistanceReciprocity TheoremNodal Analysis in Electric CircuitsMaximum Power Transfer TheoremDelta - Star transformation | Star - Delta TransformationMagnetic FieldMagnetic FluxMagnetic PermeabilityHysteresis LoopMagnetic Field and Magnetic Circuit | Magnetic MaterialsMagnetic SaturationEnergy Stored in a Magnetic FieldStatic Electric Field | Electrostatic Induction A Current Carrying Conductor Within A Magnetic FieldMagnetic SusceptibilityHard Magnetic MaterialsSoft Magnetic MaterialsMagnetic Circuit with Air GapElectric ChargeCoulombs Law | Explanation Statement Formulas Principle Limitation of Coulomb’s LawElectric Lines of ForceWhat is Electric Field?Electric Field Strength or Electric Field IntensityWhat is Flux? Types of Flux?Electric FluxElectric PotentialCapacitor and Capacitance | Types of CapacitorsEnergy Stored in CapacitorCharging a CapacitorDischarging a CapacitorFourier Series and Fourier TransformTrigonometric Fourier SeriesAnalysis of Exponential Fourier SeriesParity GeneratorElectric Circuit and Electrical Circuit ElementsSeries Parallel Battery CellsRL Series CircuitWhat is Inductor and Inductance | Theory of InductorRLC CircuitThree Phase Circuit | Star and Delta SystemRL Parallel CircuitRL Circuit Transfer Function Time Constant RL Circuit as FilterConstruction of AC Circuits and Working of AC CircuitsSeries RLC CircuitParallel RLC CircuitResistances in Series and Resistances in ParallelResonance in Series RLC CircuitPlanar and Non Planar Graphs of CircuitClipping CircuitMutual InductanceSelf InductanceSI System of UnitsElectrical International SymbolElectric Power Single and Three Phase Power Active Reactive ApparentVector Algebra | Vector DiagramRelationship of Line and Phase Voltages and Currents in a Star Connected SystemVector Diagram | Three Phase Vector DiagramTypes of Resistor Carbon Composition and Wire Wound ResistorVaristor Metal Oxide Varistor is Nonlinear ResistorCarbon Composition ResistorWire Wound ResistorVariable Resistors | Defination, Uses and Types of Variable ResistorsLight Dependent Resistor | LDR and Working Principle of LDRSource of Electrical EnergyVoltage SourceIdeal Dependent Independent Voltage Current SourceVoltage or Electric Potential DifferenceVoltage in SeriesVoltage in ParallelVoltage Drop CalculationVoltage DividerVoltage MultiplierVoltage DoublerVoltage RegulatorVoltage FollowerVoltage Regulator 7805Voltage to Current ConverterNew Articles Collecting Oil Sample from Oil Immersed Electrical EquipmentCauses of Insulating Oil DeteriorationAcidity Test of Transformer Insulating OilMagnetic FluxRing Counter