Series and Parallel Circuits

Series and Parallel Circuits are common in any electronic or electrical circuits. Resistors may be connected either in series or in parallel as per the function of the circuit. The total resistance of such resistors will not be the same for series and parallel connection.

Series Connection

The name series and parallel circuits has different significance. The series circuit consists of components such as resistors, diodes, switches inline i.e., all the components are connected in sequence. What will happen when they are connected in sequence? Suppose we have connected resistors of different values in series, then if some voltage is applied to the circuit some current flows in the circuit. The current is same through all the components. Each resistor has some voltage drop.

Consider a circuit shown below which is connected in series.

Resistor in Series
Resistor in Series

Now the voltage drop across the resistors R1, R2, R3 are V1 = IR1, V2 = IR2, and V3 = IR3.

In terms of expression we can write,

VT = V1 + V2 + V3 = I (R1 + R2 +R3)

RT = R1 + R2 + R3

Where VT = Total voltage applied

RT = Total resistance

I = current flowing through circuit

In series circuit we can observe that the resistance value increases as number of resistors increases. One of the disadvantages of series connection if one of the resistance burns up then there is no flow of current i.e. it becomes open circuit. This can be eliminated by using parallel circuit.

Simple Example

By observing below circuit the resistors are connected in series the following equation is

R = R1 + R2

Resistors in Series
Resistors in Series

Where, R1 = 10Ω

R2 = 30Ω

R1 + R210Ω + 30Ω = 40Ω

In series circuit we can observe that the resistance value increases one of the disadvantages of series connection if one of the resistance burns up then there is no flow of current this can be eliminated by using parallel circuit.

Parallel Connection

In parallel connection all the nodes are connected in common. Hence in parallel circuits the voltage is same at any node. In parallel connection the current divides in each branch. The below circuit shows the parallel connection of a resistor.

Resistor in Parallel
Resistor in Parallel

As you can see that current divides in each branch of circuit. There are multiple loops for parallel connection and hence

The total current I is divided into 3 parts I1, I2, I3

At each node the current is given by:

I1 = V/RI1 = V/R1 ;  I1 = V/R

Now total current is given by IT = I1 + I2 + I3

resistance_formula_parallel

The main advantage of parallel circuit is if one of branch fails, the rest of the branches will function without any fault.