The Physics Classroom Tutorial, Static Electricity Chapter, Lesson 4.Readings from The Physics Classroom Tutorial To use the electric field equation, Coulomb’s law equation, and Newton’s laws to analyze physical situations that involve electric fields and to solve physics word problems associated with such situations. To construct and to interpret electric field line diagrams for isolated charges and for collections of two or more charges.To use an understanding of the convention for electric field direction to identify the electric field direction around a source charge.To state the mathematical definition of electric field (force/charge) and to describe the dependence of the electric field strength upon the variables that affect it.To understand that all sources of charge create an influence or action upon other objects some distance away and that the electric field concept is used to describe that influence.However, they would eventually redistribute in a way to attain a uniform charge distribution, where the electric field would only be normal to the surface, eliminating its tangential(surface) component.Teacher Toolkits » Electric Fields » Electric Fields - Complete Toolkit If this wasn’t the case, then the electric field would exert a force on the charges on the surface of the conductor which would render them non-static since they would move around. In the same way, let us attempt to understand the reason why static field lines are always normal to a conductor surface. This is because the field B inside the material is much stronger than that of the magnetizing field $B_0$ due to the pulling in of a large number of lines of force with the field lines being uniform and parallel along the magnetic material. This implies that they always travel normal to the surface of the ferromagnet and not along the surface. The key here is that the field lines travel “through” the material. This also means that the magnetic field lines find it easier to travel through the ferromagnet than pass through the free space surrounding it. This means that ferromagnets allow or pull in external magnetic field lines and allow them to pass through their material. Now, the relative permeability of ferromagnets is $\mu_r >1$. Now, the ratio of the permeability of a medium to the permeability of free space is called the relative permeability. It measures the degree to which the external magnetic field can penetrate through the material. We know that when a magnetic material is placed in a magnetizing field, magnetic permeability $\mu$ helps us measure the material’s resistance to the ambient magnetic field. Let us begin by defining the term relative permeability $\mu_r$. If there was an electric field along the surface of the conductor, think of what would happen when the charges experience a force. As for the analogy, we know that the surface of an electric conductor inherently contains static charges at equilibrium. In such a case, think of how the field lines are incident on the magnet’s surface. Hint: We know that ferromagnets allow external magnetic field lines to pass through them.
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