Dept. of Biomed. Eng. BME207: Basic Electronic Circuits Kyung Hee Univ.

http://www.ejwoo.com 1 Eung Je Woo

Charge, Electric Field and Po-tential

Eung Je Woo

Department of Biomedical EngineeringKyung Hee University

ejwoo@khu.ac.kr

Dept. of Biomed. Eng. BME207: Basic Electronic Circuits Kyung Hee Univ.

http://www.ejwoo.com 2 Eung Je Woo

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

Dept. of Biomed. Eng. BME207: Basic Electronic Circuits Kyung Hee Univ.

http://www.ejwoo.com 3 Eung Je Woo

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 vibrate• Polar molecule with no net charge may have dipole moment and rotate

•Mass•Charge•Size•Position

, , ,m Q dr

Dept. of Biomed. Eng. BME207: Basic Electronic Circuits Kyung Hee Univ.

http://www.ejwoo.com 4 Eung Je Woo

Field• Space with nothing

Qx

yz

0

Qrr

• Space with a single charged particle• Space with two charged particles• Space with multiple charged particles• Space with a charge density distribution

Dept. of Biomed. Eng. BME207: Basic Electronic Circuits Kyung Hee Univ.

http://www.ejwoo.com 5 Eung Je Woo

Potential or Voltage• Space with electric field E(r)

Qrr1

• Put a point charge at r1 from the infinity (a reference point)

• Move the point charge from r1 to r2

E(r)

Qrr2