Magnetism produces lines of force called flux. These can be detected by the compass needle which indicates the direction you are moving when the Earth's magnetic north pole attracts the north ends of the other magnets. Magnetic lines of force start from the north pole and end at the south pole. They are continuous throughout the body of the magnet. Magnetic lines of force can pass through iron more easily than air, which is why iron is used as the core in electromagnets. Two magnetic lines of force cannot cross each other, so when you try to push two identical magnets facing each other (pushing north and north towards each other), they will repel each other. Magnetic field lines attempt to contract longitudinally and tend to expand laterally. The magnetic field lines are grouped near the pole where the field is strong and away from the magnet where the field is weak. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”? Get the original essay Flux density is the amount of magnetic, electric or other flux passing through a unit area and the magnetic field strength is the force field created by moving electric charges and magnetic dipoles. Magnetic field lines fictitious objects, they are conceptualized to indicate the magnetic field on a magnetic material. They give a visual representation of the magnetic field around a magnetic material. They start in the north and end at the south pole of a magnet. A tangent to a magnetic line gives the direction of the force on a north pole. The magnitude of the force is given in terms of the density of the magnetic lines at that point. The relationship between flux density and field strength is: the higher the density of the flux lines, the greater the magnetic force. These are called lines of force. Electromagnets also have these lines, but they are electric lines of force and are similar, although the electromagnetic magnetic poles are replaced by electric charges. Electromagnetic induction is an incredibly useful phenomenon with a wide variety of applications. Induction is used in the production and transmission of energy. An eddy current is a swirling current established in a conductor in response to a changing magnetic field. The current swirls in such a way as to create a magnetic field opposing the change, to do this in a conductor the electrons swirl in a plane perpendicular to the magnetic field. Because eddy currents tend to oppose each other, they cause energy loss. Eddy currents transform more useful forms of energy such as kinetic energy into heat. This is normally less useful in most situations, as the loss of useful energy is undesirable. There are, however, some practical applications for useful energy loss. One of these applications concerns the brakes of certain trains. When a train brakes, the metal wheels are exposed to a magnetic field from an electromagnet, generating eddy currents in the wheels. This magnetic interaction between the applied field and the eddy currents acts to slow the wheels. The faster the wheels spin, the stronger the effect. This means that when the train slows down, braking force is reduced, producing the smooth stopping motion you experience on trains. Keep in mind: this is just a sample. Get a personalized article from our expert writers now. Get a personalized essay When we take a..