Series and parallel tesistances

Resistances in Series

Definition :-    

    Imagine two or more resistors in series, i.e. connected one after another so that the same current flows through them. The total resistance of the collection is the sum of individual resistances. 

    Suppose a current i flows through the resistances. The potential difference V between the points P and Q is the sum of voltage differences across the sequence of resistors, i.e., i( R1 +  R2  +  R3  +.............+ Rn ), and the current flowing is i, so that the resistance is

( V / i )    =   R    =   R1  +  R2   +  R3  +  ..............   +  Rn  .......................(1

Total resistance calculation click here

        http://www.ncert.nic.in/html/learning_basket/electricity/electricity/current%20electricity/resis_calculation.htm

Resistance in Parallel

        In the given figure, we show 3 resistors connected 'in parallel' with one another. In this  case, the current flowing into P is divided among the 3 resistors:

i = i1 + i2 + i3

However, the potential difference across any resistors  is the same, namely

i1 R1 = i2 R2 = 13 R3

These equations can be thought of as determining the currents i1, i2, i3.

Substituting, We have

i = ( V/R1 + V/R2 + V/R3 ) = V / R 

or

1/R1 + 1/R2 + 1/R3 = 1 / R. 

Similarly, For n number of resistors connected in parallel,

    The Total Equivalent resistance = 1/R1 + 1/ R2 +.......+ 1/Rn = 1 / R. 

Watch:

    

Voltage and          current:https://eeedear.blogspot.com/2019/04/difference-between-voltage-and-current.html?m=1

Ohms law:https://eeedear.blogspot.com/2019/04/basic-of-eee-ohms-law.html?m=0