APHY202 9/21/2015 1 17.7 Capacitance Ratio of the charge on a conductor to the potential...

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APHY202 06/27/22 1 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 Q C

Transcript of APHY202 9/21/2015 1 17.7 Capacitance Ratio of the charge on a conductor to the potential...

Page 1: APHY202 9/21/2015 1 17.7 Capacitance   Ratio of the charge on a conductor to the potential difference between the conductors.   Units of farads (F)

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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

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