• Magnetic fields have direction. As a result we must pay special attention to directions, and vector calculations.
• Magnetic fields pass through space.
• resistivity of materials decreases with temperature
• Amperes Circuit Law
• Flux density can be calculated for low H values. As the value climbs the relationship becomes non-linear.
• Permeability is approximately linear for smaller electric fields, but with larger magnetic fields the materials saturate and the value of B reaches a maximum value.
Figure 23.1 Saturation for a mild steel (approximately)
Figure 23.2 Magnetization curves (Sen, 1989)
• Flux density about a wire
• Flux and flux density,
• When a material is used out of the saturation region the permeabilities may be written as reluctances,
• Electric circuit analogy
• Faraday’s law,
• Field energy,
• Force can be derived from the energy,
• The basic property of induction is that it will (in the presence of a magnetic field) convert a changing current flowing in a conductor to a force or convert a force to a current flow from a change in the current or the path.
Figure 23.3 The current and force relationship
• We will also experience an induced current caused by a conductor moving in a magnetic field. This is also called emf (Electro-Motive Force)
Figure 23.4 Electromagnetically induced voltage