Post on 28-Dec-2015
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17.7 Capacitance Ratio of the charge on
a conductor to the potential difference between the conductors.
Units of farads (F) Usually in μF or pF (10-
12 F)
V
QC
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17.7 Capacitance For a parallel-plate capacitor:
Applications: cameras, computers, TVs, noise filters, starter motors, etc.
d
AC o
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17.8 Dielectrics
An insulating material placed between plates of a capacitor that increases the capacitance: C = κCo
The polarization of the dielectric will cause an decrease in the electric field.
Application: measure humidity in air
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17.9 Storage of Electric Energy
Work done to move Δq through V is ΔW= VΔq
Total work = ½QV
PE stored = ½QV = ½CV2 = Q2/2C
The energy is stored in the electric field between the plates with a density of ½ εoE2.
Defibrillators
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17.9 Storage of Electric Energy
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1) Battery Compartment2) Capacitor
3) Transformer
4) Capacitor
5) Diode
6) Transformer
7) Neon Indicator Light8) Capacitor
9) Resistor
10) Flash Tube
11) Transistors
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17.11 The Electrocardiogram
Cell area ~ 105 m2
Charge per surface ~ 10-8 C
Depolarization
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17.11 The Electrocardiogram
04/19/23 8APHY202