Magnetism is the property of changed particles in motion due to the spin of electrons within the atoms. It is a property of materials that respond to an applied magnetic field.
Electromagnetism is the study of the interaction between electrically charged particles and magnetic fields.
A magnet is an object that can attract or repel pieces of materials with magnetic properties. The magnetic field is the area that a magnet influences.
RetentivityAbility of a magnetic material to retain itsmagnetism after it has been magnetized
Magnets were named after Magnesia, in Asia Minor, where the Greeks discovered metallic rocks that could attract metal and other rocks.Early peoples called magnets lodestones. These stones were used in navigation as compasses, therefore they were called lodestones, from the words lode (meaning course or way) and stone.
Classification of Different Magnetic Materials1. Ferro Magnetic- Substances that are highly attracted by magnets2. Non-Ferro Magnetic – non-magnetic substance3. Diamagnetic – materials are slightly repelled by a magnet4. Paramagnetic – slightly attracted by powerful magnets
Classification of Magnets2. Natural3. Artificial4. Electromagnet
General Properties of Magnets1. Magnets usually have two poles2. Like magnetic poles repel and unlike poles attract3. A piece of magnetite when made to hang freely would align itself with the magnetite field of the earth following the N.S. direction4. Permanent magnets are magnets made from alloys of cobalt and nickel5. Other metal like iron can be magnetized by interaction
Causes of Magnetism1. Molecular Theory2. Electron Theory3. An electron revolving around the nucleus gives the atom a magnetic property4. The electron opening at its own axis becomes a tiny permanent magnet
Scientists with ImportantContributions to the Field of Electromagnetism
Hans Christian OerstedDanish scientist who proved the relationship between magnetism and electricity
William GilbertThe scientist who made the earliest investigation to the discovery of the many properties of natural and artificial magnets
Andre Marie AmpereFormulated laws on electromagnetic forces based on his experiments
Heinrich Friedrich Emil LenzFormulated Lenz’s law, for determining the sign and direction of an induced current or voltage.
Michael FaradayDiscovered electromagnetic induction.
Lenz’s LawThe direction of an induced current (andhence, induced voltage) is opposite thedirection of what causes it.
Faraday’s LawThe induced EMF in a coil is proportional to the product of the number of loops and the rate at which the magnetic flux changes within the loops.
Coulomb’s Law of MagnetismThe force between two magnetic poles isdirectly proportional to the products of thestrength of the poles and inversely proportionalto the square of the distance between them.
Right Hand Rule Point the fingers to the direction of the magnetic field and the thumb to the direction of the velocity of a positive charge. The palm then points to the direction of the force on the charge.