(2.4) thatIf one now imagines that the exciting current i varies with time, Eq. 2.1. In Figure 1, the current and magnetic field obey the right-hand rule. Your IP: 85.187.128.12 The Magnetic Field (H-Field) Encircles an Electric Current. due to electric charge. If I Amps are flowing through a straight wire, the magnetic field that surrounds the wire a given by: Equation [1] states that the magnitude of the magnetic field decreases with distance as 1/R from the wire. It is, therefore, seen that by certain simplifying assumptions and field symmetries, it has been possible to lump the distributed magnetic system into a lumped magnetic circuit described by Eq. (2.6) would indicate that Hc will vary in unison with it. It is stated as: Imagine that you are holding a current carrying conductor in your right hand with the thumb pointing in the direction of current. Such description apart from being highly complex is otherwise not necessary for use in electric machines wherein the fields (magnetic and electric) are slowly varying (fundamental frequency being 50 Hz) so that the displacement current can be neglected. The Electric Field arises The effect of the leakage flux is incorporated in machine models through the concept of the leakage inductance. wraps around the wire. The Magnetic The Magnetic Circuits field intensity H causes a flux density B to be set up at every point along the flux path which is given by, The units of flux density are weber (Wb)/m2 called tesla (T). Hence, it is safe to assume that the magnetic flux set up by mmf Ni is mainly confined to the ferromagnetic core and the flux set up in air paths is of negligible value. There is no way to avoid magnetic leakage as there are no magnetic insulators in contrast to electric insulators which confine the electric current to the conductor for all practical purposes. The direction of field intensity is H and so the direction of flux Φ is determined from the Right Hand Rule (RHR). and core flux (assumed to be total flux) is given by, where Ac = cross-sectional area of core and flux in the limbs is oriented normal to cross-sectional area. You do not need to know the meaning of this equation for A-level. Suppose now that the electric charges are moving. In the world of electromagnetics, there are two main types of fields. will be far larger in the Magnetic Circuits core in Fig. Furthermore, in this topic, you will learn about the magnetic field, magnetic field formula, its derivation, and solved examples. It has been seen previously that the Magnetic Field Equation intensity along the mean flux path in the core can be regarded constant at Hc. Often we either only deal with a magnetic field or an electric field. vector quantity like the Electric as shown in Figure 1: Figure 1. 2.2, while inductive effects are bound to appear in an electric circuit. 2 2 wherein (mmf) is analogous to E (emf), R (reluctance) is analogous to R (resistance) and Φ (flux) is analogous to i (current).The analogy though useful is, however, not complete; there being two points of difference: (i) magnetic reluctance is nondissipative of energy unlike electric resistance. In case of a coil you imagine that you are grasping the coil in right hand with the thumb in the direction of current; then the fingers curl in the direction of flux. This simplified field picture is a consequence of negligible displacement current in slowly-varying fields as mentioned earlier. It is certainly different from the magnetic flux density. 2.2 Fig. If your thumb points in the direction The magnitude of the magnetic field is given by Equation [1] and the direction doesn't point away, towards, or in the same direction as The units for the Magnetic Field are Amps/meter [A/m]. It is, therefore, seen that for a given H, the flux density B and, therefore, the flux over a given area. Around the corners, flux lines have different path lengths between magnetic equipotential planes (typical ones being ab and cd shown in Fig. The lumped magnetic circuit and its electrical analog are useful concepts provided the permeability (μ) of the core material and, therefore, the core reluctance is constant as is tacitly assumed above. Furthermore, the formation of a magnetic field takes place when a … The Magnetic field is also directly proportional to the current I.The Magnetic field is a vector quantity like the Electric Field.