Charge, Electric Field and Potential

Eung Je Woo

Department of Biomedical Engineering

Impedance Imaging Research Center (IIRC)

Kyung Hee University

Korea

ejwoo@khu.ac.kr

IIRC, Kyung Hee Univ. February, 2015

2

Fundamental Quantity• 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)

• Mechanics

• Electromagnetics

• Optics

• Thermodynamics

• Chemistry

IIRC, Kyung Hee Univ. February, 2015

3

Charged Particle and Charge Den-sity• Free electron and hole are mobile• Unbounded ion and molecule are mobile• Bounded atom and molecule are immobile but may vibrate• Polar molecule has no net charge but dipole moment and may rotate

• Mass• Charge• Size• Position

, , ,m Q dr

IIRC, Kyung Hee Univ. February, 2015

4

Electric Field• 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

Qx

y

z

0

Qrr

IIRC, Kyung Hee Univ. February, 2015

5

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

Qrr1

E(r)

Qrr2

EOD