Series Circuit
The circuits where many resistances are connected end to end so that the current flows through only one path is popularly called a series circuit.
Table of Contents
Consider the resistances R1, R2, and R3 ohms that are connected in series across a battery source of V volts as shown. Thus, there remains only a single path for the current ‘I’ to flow. By Ohm’s law, the voltage across the various resistances is
V1 = I R1,
V2 = I R2,
V3 = I R3
Now, V = V1 + V2+ V3
= I R1 + I R2 + IR3
= I (R1 + R2 + R3)
or V/I = R1 + R2 + R3
But V/I is the total resistance RS between points A and B. Note that RS is called the total or equivalent resistance of all the resistances connected in the series circuit.
The total or equivalent resistance is the virtual single resistance, which if substituted for the series resistances, would result in the same current throughout the circuit.
The total conductance GS of the series circuit which is also the inverse of the total resistance, given by:
GS = 1/Rs = 1 / (R1 + R2 + R3)
Or, 1/Gs = 1/G1 + 1/G2 + 1/G3
Characteristics of series circuits
The important characteristics of a series circuit are:
The current is the same at each resistor of the series circuit.
The total resistance in the circuit is equal to the mathematical addition of all the values of individual resistances.
The total power dissipated in the series circuit is almost equal to the sum of powers dissipated in individual resistances neglecting the idealistic characteristics. This also holds true for the parallel and series-parallel circuits. Thus referring to Fig above,
RS = R1 + R2 + R3
or I2RS = I2R1 + I2R2 + I2R3
or PS = P1 + P2 + P3
A series resistance circuit can also be considered a voltage divider circuit because the potential difference across any one resistance is a fraction of the total voltage applied across the combination of series, the fraction depends on the values of the resistances.
Advantages of series circuits:
Simple in design: These circuits are simple in design as all the connections of its components are end-to-end connections.
Voltage Sharing: The Series circuit helps with the voltage division as the total voltage is subdivided among the various components of the circuit making it beneficial for components requiring different voltage levels for functioning.
Current Control: The current control is easier as it can be done just by adding a resistor.
Cost-effective: These circuits are cost-effective as they require less wiring compared to a parallel circuit.
Less heat dissipation: In these circuits, the total resistance is generally large because of the series arrangement. However, the current is significantly lower, which makes the heat dissipation very less compared to parallel circuits.
Application of series circuit:
The application of this type of circuit is seen in refrigerators, freezers, heaters light bulbs, etc. The string lights or Diwali lights also include the use of a series circuit, in which if one light fails, the entire string won’t light up, indicating a failure to be fixed.
These are used for battery-boosting purposes. Batteries connected in series achieve a higher total voltage required for powering up high-voltage loads.
These circuits are utilized in electrical heating where all the heater elements are connected in series so that the current through each element remains the same which provides consistent heating.
Basic Alarm circuits often utilize these arrangements for different components and sensors to give out an alarm when the circuit is broken.
