Section 1 5 TRƯỜNG ĐIỆN TỪ

No Slide Title Slide Presentations for ECE 329, Introduction to Electromagnetic Fields, to supplement “Elements of Engineering Electromagnetics, Sixth Edition” by Nannapaneni Narayana Rao Edward C Jor[.]

Slide Presentations for ECE 329, Introduction to Electromagnetic Fields, to supplement “Elements of Engineering Electromagnetics, Sixth Edition” by Nannapaneni Narayana Rao Edward C Jordan Professor of Electrical and Computer Engineering University of Illinois at Urbana-Champaign, Urbana, Illinois, USA Distinguished Amrita Professor of Engineering Amrita Vishwa Vidyapeetham, Coimbatore, Tamil Nadu, India 1.5 The Electric Field 1.5-3 The Electric Field is a force field acting on charges by virtue of the property of charge Q1Q2 Coulomb’s Law F1  a 21 F2 a12  R Q R F1 a21 Q1 Q2 Q1 F2  a12 4 R   permittivity of free space 10 –9  F/m 36 1.5-4 D1.13(b) Q 2a a Q Q2/40(2a2) Q2/40(4a2) Q2/40(2a2) Q Q  4 Q From the construction, it is evident that the resultant force is directed away from the center of the square The magnitude of this resultant force is given by 1.5-5 Q2 Q  cos 45  2 4  2a  4  4a  1   2 2a 4a 0.957  N a 1.5-6 Electric Field Intensity, E is defined as the force per unit charge experienced by a small test charge when placed in the region of the field F E E Lim qE q q –q q –qE Thus Fe qE Units: N N – mSources: V Charges;   Time-varying C C•m m magnetic field 1.5-7 Electric Field of a Point Charge Qq F a R 4  R (Coulomb’s Law)  Q  q  a R  4  R  q E due to Q  Q  E due to Q  a R 4  R R Q q aR 1.5-8 Constant magnitude surfaces are spheres centered at Q Direction lines are radial lines emanating from Q E R aR Q E due to charge distributions (a) Collection of point charges E n  Qj  R j j 1 Q1 a Rj aRn R1 R2 R3 Q2 Q3 Qn Rn aR aR2 aR1 1.5-9 Ex z Q (> 0) d d2 + x2  e d d2 + x2 Q (> 0) y x Electron (charge e and mass m) is displaced from the origin by  (