Electric Current

Conductors: The materials that allow electric current to pass through them.
Examples: Iron nail, copper wire, brass key, aluminium rod, pencil lead (graphite), mercury..etc. 
*All metals are good conductors of electricity.
*Human body is good conductor of electricity.
*All liquids are bad conductors of electricity except mercury which is a liquid metal.
*Pure water is a bad conductor of electricity.

Insulators (or) Non-conductors: 
The materials which does not allow electric current to pass through them.
Ex: Paper, wood, plastic, cloth, eraser (rubber), pure water....etc.
Conductors of electricity are coated with insulators to prevent leakage of electricity.,

Semiconductors: 
The materials which allows electricity partially to pass through them is called semiconductors
Ex: Silicon , germanium.. etc

Symbols used in Electrical circuits:    
        Device                                    Symbol
1.An electric cell                              
2.An electric bulb                                                  
3.A plug key (as a switch)                                   
4.A tap key (as a switch)                              
5.A voltmeter                                            
6.An Ammeter                               
7.A resistance                               
8.A Rheostat                                
9.A fuse