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ECE 303 – Fall 2005 – Farhan Rana – Cornell University
Lecture 6
Capacitance
In this lecture you will learn:
• Capacitance
• Capacitance of Some Simple Structures
• Some Simple Solutions of Laplace’s Equation
ECE 303 – Fall 2005 – Farhan Rana – Cornell University
Capacitance
Consider two metallic objects connected by a voltage source
V
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• The total charge on both metal objects have the same magnitude but opposite sign
• The charge is proportional to the applied voltage:
V
Q
∝
total charge +
Q
total charge 
Q
• The constant of proportionality is called the capacitance
C
:
CV
Q
=
• Capacitance has units
Coulombs/Volts
or
Farads
• More generally, capacitance is also defined as:
dV
dQ
C
=
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