Electricity & Magnetism PDF

ELECTRICITY & MAGNETISM Electricity- is a form of energy resulting from the movement of charged particles, the electrons.  Static Electricity-whe n electric charges accumulate on the surface of material, often through friction Van de graaff generator creating...

ELECTRICITY & MAGNETISM Electricity- is a form of energy resulting from the movement of charged particles, the electrons.  Static Electricity-whe n electric charges accumulate on the surface of material, often through friction Van de graaff generator creating potential difference.  Current Electricity-the flow of electric charge through a conductor. This is driven by voltage. Direct current (DC) Alternating current (AC) Magnetism- is the study of magnetic fields and their effect on materials. This effect, due to unbalanced spin of electrons in atoms. Electricity and magnetism are closely related. Flowing electrons produce a magnetic field, and spinning magnets cause an electric current to flow. HISTORY OF MAGNET In a distant land in Asia Minor, thousands of years ago, the Greeks discovered that certain metallic rocks (lodestones) in the district of Magnesia could attract or repel similar rocks. They referred to these rocks as magnets in honor of the place where the rocks were discovered. ? The English man William Gilbert (1540-1603) was the first to investigate the phenomenon of magnetism systematically using scientific methods. He also discovered that the Earth is itself a weak magnet Magnetic field – is a region in space in which a magnetic force can be detected. ? Magnetic flux – the number of magnetic field lines per area ? Tesla (T) – SI unit of magnetic field strength in honor of physicist Nikola Tesla PROPERTIES OF MAGNETS ? Magnets have the ability to attract materials that are magnetic in nature.  Classification of Materials (according to how they are affected by the magnetic field) Which will be attracted most to a magnet? Tell whether the given example is Ferromagnetic, Paramagnetic or Diamagnetic:  FERROMAGNETIC ? materials which are strongly attracted to magnets. Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins and line up parallel with each other in a region called a domain. E.g. iron. nickel, cobalt, steel, gadolinium.  PARAMAGNETIC ? materials which have a small positive susceptibility to magnetic fields. They are slightly attracted to magnets. E.g. aluminum, platinum, chromium sulphate, crown glass  DIAMAGNETIC ? materials create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. E.g. Gold, silver, copper, mercury, quartz, water, alcohol, air, bismuth, antimony, cloth and fabric. ? When allowed to hang freely, magnets always align in one particular direction. ? Like poles repel and unlike poles attract. REPULSION ATTRACTION ? Magnetic poles always occur in pair. MAGNETS OF DIFFERENT SHAPES  USES: ? Horseshoe magnets – bar magnets bent in a U shape ? Makes the magnet stronger by pointing the poles in the same direction ? Small horseshoes can collect paper clips, industrial-sized horseshoe magnets are used in construction and engineering to pick up large pieces of heavy metals ? Also used at the bottoms of pendulums  USES: ? Ring magnets - round with a hole in the middle, and because of this shape they are sometimes referred to as donut magnets. ? used in science experiments such as a demonstration of magnetic repulsion where the magnetic rings are threaded through a wooden pole. When the same poles of the magnets face each other they won’t touch  USES: ? Cylindrical magnets - used in medicine. Some doctors experiment with magnetic rods to treat scoliosis patients  USES: ? Bar magnets – magnet’s power is focused at the poles and lessens at the sides. ? Generally the weakest shapes because the poles have the smallest area ? Most common shape used in everyday life such as refrigerator magnets and compasses.  USES: ? Disc magnets - because of the wide, flat surface, disc magnets have a large pole area making them strong, effective magnets. ? used every day in clothing, fashion accessories, and home decor. Sewing disc magnets into clothing is a great way to hold fabric together. Industrial-sized disc magnets are commonly used to pick up old cars at junkyards.  KINDS OF MAGNET ? Permanent magnets – are those we are most familiar with, such as the magnets hanging onto our refrigerator doors. They are permanent in the sense that once they are magnetized, they retain a level of magnetism. ? Temporary magnets – are those which act like a permanent magnet when they are within a strong magnetic field,but lose their magnetism when the magnetic field disappears. Examples would be paperclips, nails and soft iron items.