Dept. of Biomed. Eng.
BME207: Basic Electronic Circuits
Kyung Hee Univ.
Charge, Electric Field and Potential
Eung Je Woo
Department of Biomedical Engineering
Kyung Hee University
ejwoo@khu.ac.kr
http://www.ejwoo.com
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Eung Je Woo
Dept. of Biomed. Eng.
BME207: Basic Electronic Circuits
Kyung Hee Univ.
Fundamental Quantity
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Length (dimension or size) in meter (m)
Time (sequence or duration or interval) in second (s)
Mass in kilogram (kg)
Charge in coulomb (C)
Temperature in kelvin (K)
Amount of substance in mole (mol)
Luminous intensity in candela (cd)
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Mechanics
Electromagnetics
Optics
Thermodynamics
Chemistry
http://www.ejwoo.com
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Eung Je Woo
Dept. of Biomed. Eng.
BME207: Basic Electronic Circuits
Kyung Hee Univ.
Charged Particle and Charge Density
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Free electron and hole are mobile
Unbounded ion and molecule are mobile
Bounded atom and molecule are immobile but vibrate
Polar molecule with no net charge may have dipole moment and rotate
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Mass
Charge
Size
Position
 m, Q, r, d 
http://www.ejwoo.com
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Eung Je Woo
Dept. of Biomed. Eng.
BME207: Basic Electronic Circuits
Kyung Hee Univ.
Field
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Space with nothing
Space with a single charged particle
Space with two charged particles
Space with multiple charged particles
Space with a charge density distribution
z
r
Qr
y
x
Q
http://www.ejwoo.com
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Eung Je Woo
Dept. of Biomed. Eng.
BME207: Basic Electronic Circuits
Kyung Hee Univ.
Potential or Voltage
• Space with electric field E(r)
• Put a point charge at r1 from the infinity (a reference point)
• Move the point charge from r1 to r2
E(r)
r2
Qr
r1
http://www.ejwoo.com
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Qr
Eung Je Woo