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### 26 Cards in this Set

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 Is the north magnetic pole of the earth a north polarity or a south polarity? The north magnetic pole is located near the southern polar axis and the magnetic south pole is located near the northern polar axis. (p104 - 105) What were early natural magnets known as? Because they are always able to align themselves north and south, natural magnets became known as “leading Stones” or lodestones. (p104) The south pole of one magnet is brought close to the south pole of another magnet. Will the magnets repel or attract each other? If like poles of the two magnets are brought together, they repel each other. (p109) How can the polarity of an electromagnet be determined if the direction of current flow is known? Using the left hand rule is used for determining polarity of an electromagnet when the direction of the current is known. Flux Density The number of magnetic lines contained in a certain area. The area of measurement depends on the system of measurement (p114) Permeability is a measure of a material’s ability to become magnetized. Example if a core material causes the magnetic field to become 10 times stronger, then the core material has a permeability of 10. The standard is air which is 1 (p112) Reluctance is the resistance to magnetism. example: soft iron or steel has a high permeability and a low reluctance because it is easily magnetized. A material such as copper has a low permeability and high reluctance. (p112) Saturation When the current flow in an electromagnet is continually increased, the magnet eventually reaches a point where its strength increases only sightly with an increase in current. This occurs when all the molecules of the magnetic material are lined up. (p112) Coercive Force is the measure of a material’s ability to retain magnetism. High coercive force is desirable in materials that are intended to be used as permanent magnets. Low coercive force is generally desirable for materials intended to be used in electromagnets. (p113) Residual Magnetism When current flow through a coil of a magnet is stopped, some magnetism may be left in the core material. The amount of magnetism left in a material after the magnetizing force has stopped. (p112) Flux What magnetic lines of force are called. The symbol used is phi Whenever an electric current flows through a conductor a magnetic field is formed around the conductor Electromagnets is dependent on the electrical current flow to produce a magnetic field. They are generally designed to produce a magnetic field only as long as the current is flowing; they do not retain their magnetism when current flow stops. How do electromagnets operate on the principal that current flowing through a conductor produces a magnetic field around the conductor. What happens when a conductor is wound into a coil The magnetic lines of flux add to produce a stronger magnetic field. A coil with 10 turns of wire produces a magnetic field that is 10 times as strong as the magnetic field around a single conductor. Permanent magnets are magnets that do not require any power or external force to maintain their field. they are excellent example of one of the laws of magnetism: energy is required to create a magnet field, but no energy is required to maintain a magnetic field. basic laws of magnetism 1) unlike poles attract and like poles repeal2)energy is required to create a magnetic field, but no energy is required to maintain a magnetic field. Flux Density is the measure of magnetic strength and the units are in lines per square inch what are three basic types of magnetic materials 1 Ferromagnetic - materials that are easily magnetized. iron nickel, cobalt, and manganese2. Paramagnetic - can be magnetized but not as easily as ferromagnetic materials. platinum, titanium, and chromium3. Diamagnetic - can not be magnetized. copper, brass, antimony How can an object be demagnetized 1. placing it in a AC magnetic field and pulling it away.2. by striking it.3. by heating it. Permanent magnets Are magnets that do not require any power or force to maintain their field Basic law of magnetism Energy is required to create a magnetic field, but no energy is required to maintain a magnetic field. Electromagnets Magnets that relay on electricity to become magnetized. Ferromagnetic Materials that are easily magnetized. Ex. iron nickel, cobalt, and manganese Paramagnetic Materials that can be magnetized but not as easily as ferromagnetic materials. Ex. platinum, titanium, and chromium Diamagnetic Material that can not be magnetized. Ex. copper, brass, antimony