Permeability of Free Space (µ0)

Chapter 4.7 Permeability of Free Space (µ0)

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

  • 118Fundamental Electrical and Electronic Principles Fig. 4.8 rd(a)(b) Worked Example 4.5 Q A current of 400 mA is passed through a 550 turn coil wound on a toroid of mean diameter 8 cm. Calculate the magnetic fi eld strength. A I 0.4 A; N 550; d 8 10 2 m dHN metremampere turn/metre800 255500 40211...I225875 351so At/m H.Ans 4.7 Permeability of Free Space ( 0 ) We have seen in electrostatics that the permittivity of the dielectric is a measure of the ‘ willingness ’ of the dielectric to allow an electric fi eld to exist in it. In magnetic circuits the corresponding quantity is the permeability of the material. If the magnetic fi eld exists in a vacuum, then the ratio of the fl ux density to the magnetic fi eld strength is a constant, called the permeability of free space. 0henry/metreBH(4.4)compare this to farad/metreThe value forhen00εDE410 7rry/metre0 is used as the reference or datum level from which the permea-bilities of all other materials are measured.