## Table of Contents

- Series Circuit and Parallel Circuit
- What Does a Parallel Circuit Look Like?
- Properties of Parallel Circuits
- Voltage in Parallel Circuits
- Ohm's Law in a Simple Parallel Circuit
- Resistance in Parallel Circuits
- Lesson Summary

Understand what is a parallel circuit and what does a simple parallel circuit look like. Learn about the properties of the parallel circuit & its illustration.
Updated: 11/10/2021

- Series Circuit and Parallel Circuit
- What Does a Parallel Circuit Look Like?
- Properties of Parallel Circuits
- Voltage in Parallel Circuits
- Ohm's Law in a Simple Parallel Circuit
- Resistance in Parallel Circuits
- Lesson Summary

Electrical circuits may be arranged in two basic configurations called series circuits and parallel circuits. The main difference between the two is that in parallel circuits connect devices or components in branched pathways while while series circuits connect devices in a row one after another.

In a **series circuit**, the components are connected to each other in consecutive way one after another in one big loop. In a series circuit, there is only one path through which the electricity is able to flow.

What is a parallel circuit exactly? Electricians and physicists define a **parallel circuit** as one in which each component is connected in its own branch or loop directly to the source of electricity. When the circuit is closed (with no breaks) this provides multiple different paths through which the electricity is able to flow at the same time. In an open parallel circuit, there is a break somewhere in the pathway, but since each branch is its own independent path, a break in one branch does not effect the devices in another branch. This is shown in Figure 2, which shows a simple parallel circuit.

Just what does a parallel circuit look like? The parallel circuit illustration in Figure 3 shows that each component of the electrical circuit is connected from both ends of the component directly to the source of electricity, creating its own loop or branch. Each place where a loop branches off is called a node. The current flows from the electrical or voltage source (V), usually a battery, through the nodes to each component (labeled R for resistor in the diagram) and then back to the source. So some of the current is flowing through all the components at the same time. Because each branch is independent of the others, if there is a break in one of the branches it will not effect the other components of the circuit.

There are three important properties of parallel circuits: current, voltage, and resistance.

- In a parallel circuit, the voltage across each component is the same.
- Unlike voltage however, the amount of current that flows through each branch of a parallel circuit is not the same. Current is a measure of the amount of electrons flowing in a circuit. Because each component is in its own loop, when the flow of electricity branches off into different directions at the nodes, the amount of current is divided. After passing through the components, the separated currents rejoin so that the total current is equal to the sum of the current flowing through each branch through each of the components in the parallel circuit.
- Resistance is a property of the components that oppose the flow of electricity. The total resistance in a parallel circuit is actually less than the resistance of the individual components of the circuit. Each additional component diminishes the total resistance of the circuit. This may sound counterintuitive, but it will become more clear later in the lesson.

Voltage is the result of differences in electrical potential energy. This provides the force that causes electricity to move or flow through a circuit. The more electrons there are the greater the electrical potential energy. In a parallel circuit, each component is directly connected to the power sources so the voltage at each component is the same as the source voltage.

**Ohm's Law** describes the relationship between voltage, current, and resistance. It states that the amount of current is directly proportional to the amount of voltage and inversely proportional to the resistance. Said another way, if the amount of voltage is increased, then the amount of current is also increased or if the amount of voltage is decreased then the amount of current is also decreased. On the other hand, if the amount of resistance is increased the amount of current is decreased. If the amount of resistance is decreased, then the amount of current is increased.

This relationship between current, voltage and resistance is represent by the following mathematical model, or formula:

{eq}I = \frac{V}{R} {/eq}

This formula can be used to calculate the current. If the voltage of a given circuit is 9v and the total resistance is 3, then according to Ohm's Law I = 9/3 or 3 amps

In parallel circuits, resistance diminishes with each added component. This is a result of Ohm's Law. Adding components in parallel increases the number of nodes, or points where the current branches off. So there will be less current flowing through each branch.However total current is the sum of the current through each branch.

{eq}I = I_1+I_2+I_3+... {/eq}

Since Ohm's law says the I = V/R, the total resistance can be written as:

{eq}V=\frac{V}{R_1}+\frac{V}{R_2}+\frac{V}{R_3}+... {/eq}

Factoring out the V from each term on the left gives the following:

{eq}I = V(\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+...) {/eq}

So the total resistance is {eq}\frac{1}{R} = \frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+... {/eq}

This information can be used to determine the amount of total resistance and the current for the following parallel circuit:

The voltage in this circuit is 2V. The total resistance is found using the formula from above:

{eq}\frac{1}{R}=\frac{1}{150}+\frac{1}{400}=\frac{1}{0.00916666666} {/eq}

{eq}R=109 {/eq}

Then using Ohm's Law to find current:

{eq}I = \frac{2}{109} = 0.0183A {/eq}

In **parallel circuits**, devices are connected in parallel along branched pathways , while in **series circuits** the are connected all in a row.

- The voltage at each component of a parallel circuit is the same and is equal to the voltage at the source.
- Current is divided among the branches of a parallel circuit.
- If a circuit is closed, then there are no breaks in the circuit path.
- Total current is equal to the sum of the current in each loop.
- Resistance is decreased when circuit branches are added.

**Ohm's Law** describes the relationship between current voltage and resistance. It states that current = voltage/resistance. The current is proportional to the voltage and inversely proportional to the resistance

Unlike series circuits, the devices in a parallel circuit are connected in branches that are independent of each other. This makes parallel circuits more advantageous because the independent branches mean that even if there is a break in one branch, the devices in other branches can continue to operate.

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Frequently Asked Questions

You can determine if a circuit is a parallel or series circuit by looking at connections and components. If both ends of each component are connected directly to the battery or source of electricity with no other component in between, then it is a parallel circuit.

In a series circuit, each component of the circuit does not connect directly to the batter. In a parallel circuit, each component of the circuit is connected directly to the battery or power source.

The current in an electrical circuit is the flow of electricity. In a parallel circuit the total current is the sum of each branch or loop of the circuit.

A parallel circuit is one in which both ends of each component are connected directly to the battery or source of electricity with no other component in between. Electricity flows from the source directly to each component. If the portion of the circuit to one component is broken, the other components still have complete circuits and can still operate.

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