MAGNETISM AN INTRODUCTION TOPICS MAGNET MAGNETIC FIELD MAGNETIC POLES Magnetism Magnetism is a subject that includes the properties of magnets, the effect of the magnetic force on moving charges and currents, and the creation of magnetic fields by currents. Magnetism Magnetism is a class of physical phenomena that are mediated by magnetic fields. It is a force of nature produced by moving electric charges. What causes magnetism? The same direction spin of electrons causes magnetism. (Motion of Charges) In most materials, electrons in the atoms spin around in different directions. In magnets, the electrons all spin in the same direction. The direction of the spin of the electrons determines the direction of the magnetic field. Magnet An object which is capable of producing magnetic field and attracting unlike poles and repelling like poles. Any material capable of attracting iron and producing a magnetic field outside itself. Properties of Magnet Force of attraction is maximum at the ends of the magnet. These ends are known as poles of the magnets. Whenever a magnet is suspended freely in mid-air, it always points towards the north-south direction. Pole pointing towards geographic north is known as the North Pole, and the pole pointing towards geographic south is known as the South Pole. Like poles repel while unlike poles attract. Magnetic poles always exist in pairs. The magnetic force between the two magnets is greater when the distance between these magnets is lesser. Properties of a Magnet Attractive property Directive property This property proves that the magnetic strength at the ends of the poles is strong. This property helps to understand which pole of the magnet is north and south by suspending the magnet in mid-air. Properties of a Magnet Law of magnetic poles Like poles repel while unlike poles attract. Pair property When a magnet is cut into two pieces, both the pieces will have the North Pole and the South Pole. Properties of a Magnet Sure test of magnetization: This test is conducted to check if a given rod is magnetized or not by checking either the attraction or the repulsion of the iron rod and magnet. 3 Types of Magnet 1. PERMANENT MAGNET 2. TEMPORARY MAGNET 3. ELECTROMAGNETS Permanent Magnets Magnets that are commonly used. They are known as permanent magnets because they do not lose their magnetic property once they are magnetized. Following are the ways to demagnetize the permanent magnets: Exposing magnets to extreme temperatures. The magnetic attraction between the magnet’s atoms gets loosened when they are hammered. Stroking one magnet with another will reduce the magnetic strength. 4 Types of Permanent Magnet 1. Ceramic or ferrite 2. Samarium Cobalt (SmCo) 4 Types of Permanent Magnet 3. Neodymium Iron Boron (NIB) 4. Alnico Temporary Magnets Temporary magnets can be magnetized in the presence of a magnetic field. When the magnetic field is removed, these materials lose their magnetic property. Iron nails and paper clips are examples of the temporary magnet. Electromagnets Electromagnets consist of a coil of wire wrapped around the metal core made from iron. When this material is exposed to an electric current, a magnetic field is generated, making the material behave like a magnet. The strength of the magnetic field can be controlled by controlling the electric current. Magnetic Poles Region at each end of a magnet where the external magnetic field is strongest. Planet Earth has a south magnetic pole where the north hand of the compass points upwards. (NORTH POLE) It also has a north magnetic pole where the south hand of the compass points downward. (SOUTH POLE) The movement of the electrons causes the object to have two poles, called north and south. 2 Magnetic Poles North Pole Considered to be negative South Pole Considered to be positive MISCONCEPTION ALERT: EARTH'S GEOGRAPHIC POLE VS. ITS MAGNETIC POLE GEOGRAPHIC NORTH POLE contains South Magnetic Pole north-seeking pole GEOGRAPHIC SOUTH POLE contains North Magnetic Pole south-seeking pole Magnetic Field Magnetic field is the area around a magnet in which the effect of magnetism is felt. Region around a magnetic material or a moving electric charge within which the force of magnetism acts. A vector field in the neighborhood of a magnet, electric current, or changing electric field in which magnetic forces are observable. It is produced by moving electric charges and intrinsic magnetic moments of elementary particles (electrons). Magnetic Field Symbol: B or H Unit: Tesla Base Unit: (Newton.Second)/Coulomb or Ns/C Can be illustrated in 2 different ways: Magnetic Field Vector Magnetic Field Lines Illustrating Magnetic Field Magnetic Field Vector The vector field is a set of many vectors that are drawn on a grid. Each vector points in the direction that a compass would point and has a length dependent on the strength of the magnetic force. Illustrating Magnetic Field Magnetic Field Lines Magnetic field lines are imaginary lines. Magnetic field lines are a visual tool used to represent magnetic fields. They describe the direction of the magnetic force on a north monopole at any given position The density of the lines indicates the magnitude of the field. Illustrating Magnetic Field Properties of Magnetic Field Lines Magnetic field lines never cross each other The density of the field lines indicates the strength of the field Magnetic field lines always make closed loops Magnetic field lines always emerge or start from the north pole and terminate at the south pole.
