1. Dept. of Biomed. Eng.BME207: Basic Electronic CircuitsKyung Hee Univ. http://www.ejwoo.comhttp://www.ejwoo.com 1Eung Je Woo Charge, Electric Field and Potential Eung Je Woo Department of Biomedical Engineering Kyung Hee University ejwoo@khu.ac.kr

2. Dept. of Biomed. Eng.BME207: Basic Electronic CircuitsKyung Hee Univ. http://www.ejwoo.comhttp://www.ejwoo.com 2Eung 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

3. Dept. of Biomed. Eng.BME207: Basic Electronic CircuitsKyung Hee Univ. http://www.ejwoo.comhttp://www.ejwoo.com 3Eung Je Woo Charged Particle and Charge Density 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

4. Dept. of Biomed. Eng.BME207: Basic Electronic CircuitsKyung Hee Univ. http://www.ejwoo.comhttp://www.ejwoo.com 4Eung Je Woo Field Space with nothing Q x y z 0 QrQr r Space with a single charged particle Space with two charged particles Space with multiple charged particles Space with a charge density distribution

5. Dept. of Biomed. Eng.BME207: Basic Electronic CircuitsKyung Hee Univ. http://www.ejwoo.comhttp://www.ejwoo.com 5Eung Je Woo Potential or Voltage Space with electric field E(r) QrQr r1r1 Put a point charge at r 1 from the infinity (a reference point) Move the point charge from r 1 to r 2 E(r) QrQr r2r2