Electric Flux () and Flux Density (D)

Chapter 3.4 Electric Flux () and Flux Density (D)

Fundamental Electrical and Electronic Principles Third Edition Book
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Fundamental Electrical and Electronic Principles Third Edition Book

  • Electric Fields and Capacitors 79 Hence, fi eld strength forcechargeSo, newton/coulombEFq(3.2)or, newtonFqE(3.3)where q is the charge on the particle , and not the plates. 3.4 Electric Flux ( ) and Flux Density ( D ) In the SI system one ‘ line ’ of fl ux is assumed to radiate from the surface of a positive charge of one coulomb and terminate at the surface of a negative charge of one coulomb. Hence the electric fl ux has the same numerical value as the charge that produces it. Therefore the coulomb is used as the unit of electric fl ux. In addition, the Greek letter psi is usually replaced by the symbol for charge, namely Q . The electric fl ux density D is defi ned as the amount of fl ux per square metre of the electric fi eld. This area is measured at right angles to the lines of force. This gives the following equation DAor, coulomb/metreDQA2(3.4) Worked Example 3.1 Q Two parallel plates of dimensions 30 mm by 20 mm are oppositely charged to a value of 50 mC. Calculate the density of the electric fi eld existing between them. A Q 50 10 3 C; A 30 20 10 6 m 2 DQADcoulomb/metreso C/m2362500600083 311.Ans