Ohm's Law

   

                                                          

    

  

     after watch this videos about Ohm ’s law we write some notes about it  the relation between current (I) and voltage (V) across resistance ( R )             

        

 

 

              

                                          

                                                                                                                 

 

    

                 

          

   

                           

resistance

                  Resistance

 A third factor that plays a role in an electrical circuit is resistance

All material impedes the flow of electrical current to some extent

The amount of resistance depends upon composition length, cross-section and temperature of the resistive material. As a rule of thumb, resistance of a conductor increases with an increase of length or a decrease of cross-section Resistance is designated by the symbol “R”. The unit of measurement for resistance is ohms (Ω).

 

 

          

            Resistance Circuit Symbols

Resistance is usually indicated symbolically on an electrical

drawing by one of two ways. An unfilled rectangle is commonly

used. A zigzag line may also be used

         types of resistance

  1-fixed resistance

  2- variable resistance

fixed resistance

it has constant  amount of resistive

  some figure of fixed resistor

 

 

Measuring Resistance

Resistor Color Codes

variable resistors

we can change the value of resistance

some figure of variable resistors