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RESISTANCE IN SERIES AND PARALLEL

Resistance in series

When two or more Resistors are connected ends to ends in such a way that the same current flows through them when connected to a voltage source. The resistors are said to be connected in series.

See figure 4 above

From ohm’s law  

  where = Total Resistance     and

Therefore Resistors in series is

The total resistance of two or more resistors connected in series is the sum of the resistance of each of the resistors.

For N number of resistors connected in series

Resistance in parallel

When two or more Resistors are connected sides to sides in such a way that the same voltage is  across them when connected to a voltage source. The resistors are said to be connected in parallel.

See figure 3 above

From ohm’s law 

  where = Total Resistance     and

Therefore Resistors in parallel are represented by

The total resistance of two or more resistors connected in parallel is the inverse of the  sum of the inverse of each resistance of the resistors. Inverse of(sum of(inverse of each resistance of the resistor)) .

For N number of resistors connected in parallel:

EXAMPLE

What is the value of total resistance ?

 = 2+4+4 =10Ω

What will the value be if they are connected in parallel ?

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