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The solenoid field relationship isĪnd k is the relative permeability of the iron, shows the magnifying effect of the iron core.Fields that only have a single value at a point (like the air temperature) are called scalar fields. The effect is the multiplication of the magnetic field by factors of tens to even thousands. The ferromagnetic property of the iron core causes the internal magnetic domains of the iron to line up with the smaller driving magnetic field produced by the current in the solenoid. Properties of iron core solenoidĮlectromagnets are usually in the form of iron core solenoids. (List adapted from OpenStaxCollege discussion.) Add iron core to solenoidĪn iron corehas theeffect of multiplying greatly the magnetic field ofa solenoid compared to the air core solenoid on the left. Magnetic field lines are continuous, forming closed loops without beginning or end.The magnetic field at any point is unique. a commonly used phrase is "magnetic flux density". It is proportional to the number of lines per unit area perpendicular to the lines. The strength of the magnetic field is visualized by the closeness of the lines to each other.The direction of the magnetic field is tangent to the magnetic field line at any point in space.The properties of the magnetic field lines are can be summarized by: The magnetic field lines can be thought of as a map representing the magnetic influence of the source object in the space surrounding it. The magnetic field produced by electric current in a solenoid coil is similar to that of a bar magnet. Magnetic sources are inherently dipole sources - you can't isolate North or South "monopoles". HyperPhysics***** Electricity and MagnetismĮlectric and Magnetic Sources The electric field of a point charge is radially outward from a positive charge.Įlectric sources are inherently "monopole" or point charge sources. The magnetic field lines of the Earth enter the Earth near the geographic North Pole.Ĭomparison of magnetic and electric fields In response to the Earth's magnetic field, the compass will point toward the geographic North Pole of the Earth because it is in fact a magnetic south pole. Unlike magnetic poles attract, so the north indicator of the compass will point toward the south pole of a magnet. The north pole of a magnet will tend to line up with the magnetic field, so a suspended compas needle will rotate until it lines up with the magnetic field. The needle of a compass is itself a permanent magnet and the north indicator of the compass is a magnetic north pole. The magnetic field lines of a bar magnet can be traced out with the use of a compass. A magnetic north pole will attract the south pole of another magnet, and repel a north pole. The strongest external magnetic fields are near the poles. Permanent magnets can be made from ferromagnetic materials.Īs can be visualized with the magnetic field lines, the magnetic field is strongest inside the magnetic material. The lines of magnetic field from a bar magnetform closed lines.By convention, thefield direction istaken to be outward from theNorth pole and into the South poleof the magnet.