Download Capacitors Capacitor i-v Characteristic Capacitor Values C is Open

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Capacitor
Capacitors
• A capacitor consists of two metal plates
separated by a dielectric with permittivity є.
Peter Mathys
ECEN 1400
i-v Characteristic
Capacitor Values
• Values for small capacitors range from 10 pF
(1 pF = 10-12 F) to several 100 nF (1 nF = 10-9 F)
• Larger capacitors in the range from 1 μF (1 μF
= 10-6 F) to several mF (1 mF = 10-3 F) usually
come in the form of electrolytic capacitors
which use an electrolyte in liquid or paste
form as dielectric.
• Important: Electrolytic capacitors are
polarized. Wrong polarity leads to destruction!
C is Open Circuit for dc
Energy Stored in Capacitor
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Power and Energy
Energy Stored in Electric Field
Capacitors in Parallel
Capacitors in Series
Capacitor Charge/Discharge
Differential Equation
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Differential Equation Solution
Capacitor Charge
Capacitor Discharge
Sinusoidal Waveforms
Euler’s Relation
Using Complex Numbers
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Voltage/Current Phasors
“Ohm’s Law” for Capacitors
I and V are
called phasors.
They only
depend on the
phase of the
sinusoidal
waveform and
not on the
frequency.
Impedance
Series RC Impedance
• The generalization of Ohm’s law for phasors is
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The quantity Z = R + j·X is called impedance.
R is resistance with units ohms (Ω).
X is reactance with units ohms (Ω).
Reminder: Phasors can only be used with
sinusoidal waveforms.
• The equivalent impedance Zeq of the series RC
circuit is computed as:
• For small f Zeq approaches ZC, for large f Zeq
approaches ZR=R.
Parallel RC Impedance
• The equivalent impedance Zeq of the parallel RC
circuit is computed as:
• For small f Zeq approaches ZR=R, for large f Zeq
approaches ZC.
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