is really an essential electronic component which has a definite specific resistance
. It confines the electron flow through the circuit. For making more complex resistor circuits, the resistors can be joined together in series connection or as combinations of series and parallel connection or as parallel connection. Here, we can discuss on series connected resistors
. More than one resistor which is connected together as a chain in a solo line form makes the series resistors
(shown in figure). Since they are connected in one line, the current
flow will be the same in each resistor.
That is, the current flowing into the first connected resistor will go to the second resistor and the same current will pass through the following resistors.
Thus, we can see that there will be a common current passing through every resistor because of the single path. Voltage divider circuits can be made from these series resistors circuit.
Instead of connecting resistors in series or any complicated resistors network, an equivalent resistor with equivalent resistance (REQ
) or equivalent impedance (ZEQ
) can be implemented. It will be the sum total of the individual resistors. The complexity or the combination of the network of resistors is not the depending factor but every resistor should obey the fundamental laws (Kirchhoff’s Circuit law
and Ohm’s law
So, here the equivalent resistance is given by
The important point to note is the value of the REQ
will be higher than the value of the biggest resistor in the series circuit. For example, if there are 3 resistors of the values 1Ω, 2Ω and 6Ω respectively. Then the
which is higher than the biggest resistor value 6Ω.
The current flowing through the circuit will be the equal
The Electrical conductance
is actually the reciprocal of resistance. So the total conductance of the circuit is given by
Thus, we can say that as the number of resistors increases, the value of equivalent resistance increases. This equivalent resistor will have the same outcome in the circuit when compared the original group of resistors.
When the circuit consists of equal series resistors or series impedance, the equivalent value of resistance will be the product of the total number of resistors and the value of resistor. For example, if there are three resistors of the value ‘R’, then the equivalent resistance becomes 3R.
Voltage of Series Resistors
across the each resistor connected in a series circuit is different from the current flowing through it. The voltage across each resistor in the series circuit can be calculated with the help of Ohm’s law
For the above circuit;
So, from Ohm’s law we will get the value of each resistance, current or voltage of the series circuit. If the resistor is interchanged in a series circuit, it will not affect the total power or equivalent resistance or the current.
From Kirchhoff’s Circuit law,
Total Supply Voltage = Sum of voltages across each resistor of the circuit
Advantages of Series Resistors
- Excessive heating does not occur easily.
- Simple design.
- More power devices can be added.
Disadvantages of Series Resistors
- Breakage or fault in a single point causes the failure in total circuit.
- As the number of resistors or components increases, the value of equivalent resistance or total resistance increases.