Wednesday, 3 September 2014


1.      Materials like plastic, ebonite and glass can be charged by rubbing them with suitable materials.
2.      The bodies which will produce charges identical to the charges produced on glass rod, when rubbed with silk, are called positively charged bodies.
3.      The bodies which will produce charges identical to the charges produced on ebonite rod, when rubbed with fur or cat’s skin, are called negatively charged bodies.
4.      Like charges repel each other and unlike charges attract each other.
5.      An atom s made up of three sub atomic particles, they are neutrons, protons and electrons.
6.      In a normal atom, the number of protons is equal to number of electrons, and hence atom is electrically neutral.
7.      The electrons in the outermost orbit of an element are very weekly held and are almost free to move. These electrons are called a s free electrons.
8.      When a body loses electrons due to friction, it is said to be positively charged.
9.      When a body gains electrons due to friction , it is said to be negatively charged.
10.  Conductors are the substances having a large number of free electrons , where as insulators are the substances having very few free electrons.
11.  An electroscope is a device used for  (i) detecting electric charges (ii) finding the nature of electric charges.
12.  Conductors cannot be charged by friction. Instead , they are charged by (i) conduction and (ii) Induction
13.  When an insulated conductor is brought in contact with a charged body , such that the conductor gets the same charge as the body , then electric conduction takes place.
14.  An insulated conductor gets electrically charged when held near a charged body by the phenomenon of electric induction.
15.  Lightning is caused by when oppositely charged clouds come closer to each other.
16.  Lightning strikes building when the induced charge on the top building is too high.
17.  Lightning conductor protects a building from the damage caused by the lightning, because the charge of clouds flow through it.