1. magnetism
1.1. chinese have discovered magnets in 2500bc
1.2. laws of magnetism
1.2.1. a magnets attracts magnetic substances to itself example(iron,steel,cobalt,nickel)
1.2.2. when a magnet is freely suspended, it faces north south direction
1.2.3. similar poles of magnets repel each other
1.2.4. opposite poles of magnets attract each other
1.2.5. repulsion is the surest test of magnetism
1.2.6. when a magnetized object is rubbed over an unmagnetized object, it changes to a magnet
1.2.7. when a magnet is broken each piece is complete magnet
1.2.8. magnetic force easily passes through unmagnetized objects
1.2.9. when a magnet is heated or roughly handled, it loses its magnetic properties
1.3. electromagnets
1.3.1. a magnet which operates when
1.3.2. an electric current flows around iron
1.3.3. the branch of physics
1.3.4. which deals with the relationship between
1.3.5. electricity and magnetism
1.3.6. is called electromagnetism
1.4. temporary magnets
1.4.1. the magnets which lose their magnetism
1.4.2. as soon as the cause producing them is removed
1.5. permanent magnets
1.5.1. the magnets which do not lose their magnetism
1.5.2. when the cause producing them is removed
1.6. applications of magnets
1.6.1. magnets are used for making magnetic stickers and magnetic toys
1.6.2. magnets are used in compass needles
1.7. applications of electromagnets
1.7.1. used in electric bells, telegraph, radio
1.7.2. used in fans, motors, transistor
1.7.3. used for lifting heavy iron loads
1.7.4. used for removing iron from scrap
1.8. electric bell
1.8.1. consists of
1.8.2. electromagnet
1.8.3. armature
1.8.4. contact spring
1.8.5. contact screw adjustment
1.8.6. hammer and gong
2. electricity
2.1. quantity of electric charge
2.1.1. the number of charges which drift from higher to lower potential
2.1.2. unit of electric charge- coulombs (C)
2.1.2.1. the quantity of electric charge which will deposit 0.00118 g of silver on the cathode, when passed through silver nitrate solution
2.1.2.2. magnitude on an electron= 6.25 * 10 to the power 18= C
2.2. electrical resistor
2.2.1. the friction offered to the passage of electric current by a material is called resistance of material