8.1. Types of circuits.

SERIES AND PARALLEL CIRCUITS

Differences between series and parallel circuits

A series of circuits refer to a circuit that has only one path through which current flow. In the series circuit, all the components are connected in such a way that if any fault happens in the circuit, the current will not flow through the circuit. The current in the series circuit is the same throughout the circuit.

On the other hand, parallel circuits refer to a circuit with more than one path through which current flows. In the parallel circuit, all the components have various branches for current flow; thus, the current is not the same throughout the circuit.

Advantage of series circuits

It has a simple design that is easy to understand.
It does not overheat quickly.
It has a higher output voltage so that we can add more power appliances.
It carries the same current throughout the circuit.

Disadvantage of a series circuit

If the total number of components increases in the circuit, circuit resistance will more.
If a fault occurs at one point, the total circuit will break.

DAdvantage of parallel circuits

In a parallel circuit, if any one component gets damaged, the current does not stop and continues flowing through the other components work efficiently.
In a parallel circuit, the voltage across every component is the same; therefore, all components work efficiently.
In a parallel circuit, you can easily connect or disconnect a new component without affecting the working of another component.

Disadvantage of parallel circuit

A parallel circuit requires lots of wires for connection.

Circuits can have various electrical components, but when we are learning the basics we generally only start with cells and resistors. The way that we put these resistors together is called the association of resistors. This gives us three types of basic circuits:

Series circuit

Parallel circuit

Mixed circuit.

To solve a series-parallel combination circuit, we need to find out which resistors are in series and which are in parallel. Then we can apply the equations for each case.

To perform the electrical calculations of a circuit with several resistors, we calculate the value of a single resistor, equivalent to the association of the resistors in the circuit. The circuit formed with the equivalent resistances is called an equivalent circuit. We can obtain three things from this circuit:

The currents flowing through the circuit
The potential drops across the components
The dissipated power and the delivered power

Energy balance of the circuit

Note: in all the circuits that we have seen, the power delivered by the power source must be equal to the sum of the power dissipated by each resistor, regardless of whether the circuit is a series, parallel or series-parallel combination one.

The energy balance of the circuit is:

power delivered by the power source = power consumed by the resistors

Power sources association

Associating power sources in series

Power sources are associated in series when they are on the same branch of a circuit. Power sources in series can be replaced by a single equivalent source. We must calculate the value of this source by adding the values of the separate power sources.

In the figure below you have two batteries equal in voltage 1.5V each.

Calculate the intensity of the current passing through resistance of 10 ohms.

As the generators are in series Vt=V1+V2 = 3V.

Applying Ohm's law: I=3/10=0.3A

Remember: if the positive terminal of a power source is connected to the negative terminal of the next one, the voltages of the power sources are added together. If the positive terminal of the power source is connected to the positive terminal of the next one, the voltages are subtracted.

Associating power sources in parallel

In parallel, we can only connect power sources that are equal. We do this by connecting the terminals of the same sign. In this case, the equivalent voltage is the same for each; the only effect is that we increase the time that the circuit can operate for.

In the figure below you have two batteries equal in voltage 3V each.

Calculate the intensity of the current passing through resistance of 10 ohms.

As the generators are in series Vt=V1=V2 = 3V.

Applying Ohm's law: I=3/10=0.3A

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