Circuitry 101: The Advantages & Disadvantages of a Parallel Circuit

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When it comes to electrical circuits, there are two basic varieties: series circuits and parallel circuits. The major difference between the two is the number of paths that the electrical current can flow through. Here, we’ll zero in on parallel circuits by delving into how they work and examining both their advantages and disadvantages.

What Is a Parallel Circuit?

In simple terms, a parallel circuit occurs when all connected components share the same voltage. This voltage remains equal across all connected components, allowing the electricity to travel through several different paths back to the cell. Even if there’s a broken path, the current can continue to flow uninterrupted through other paths.

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Having a hard time picturing this? Think of it this way: a parallel circuit has branching paths, allowing the current to spread to devices that are connected much like the rungs on a ladder. That is, the “current flows into one ladder “leg” and out of the other, and along the way, it branches into each rung” (via Sciencing).

Moreover, there are four main terms you’ll have to understand when dealing with parallel circuits. These terms include the following:

  • Current (I): This is the rate at which charge flows through a circuit. You can calculate the total current (RTotal) by adding together all individual branch currents. It’s important to note that the total current flowing into the branches equates to the total current flowing out of them.
  • Resistance (R): As you add more components, total resistance decreases. This happens because the current has to travel through different paths rather than a single path as it would in a series circuit.
  • Voltage (V): All connected components have equal voltage which will make your calculations easier.
  • Ohm’s Law: This refers to the relationship between current, resistance, and voltage. It’s one of the most essential formulas (V = IR) when you’re studying electrical circuits.

Parallel Circuit Examples

Since multiple devices can be connected to the same voltage without reducing their power, parallel circuits are used commonly in everyday life. A good example of how this works, in theory, is by looking at home appliances. You can switch off your TV, but your oven, refrigerator, and other appliances will still function, all because of the parallel circuit.

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Another textbook example of parallel circuits? Lighting fixtures. If you have a chandelier with multiple light bulbs, you’ll notice that one light bulb might stop working, while others continue to shine. This is possible because the current can still flow through other paths, despite one path being broken. If you drive a car, you’ll notice that your headlights are also connected in this way, allowing each headlight to shine equally as bright, but ensuring that if one headlight stops working the other (hopefully) will continue to function.

Parallel Circuit Problems

Let’s look at some formulas that will help you solve any common parallel circuit problem. From calculating resistance to understanding Ohm’s Law, we’ve got you covered.

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How to calculate resistance:

  • 1/Req= 1/R1 + 1/R2
  • How to calculate total resistance:
  • RTotal = 1 / (1/R1 + 1/R2+ . . . 1/Rn)

Let’s say a circuit has two resistors in parallel. Each has a resistance of 6Ω. Here’s how to calculate total resistance:

  • RTotal = 1 / (1/6Ω + 1/6Ω) = 1/3Ω -> RTotal = 3Ω
  • How to calculate the current:
  • I = V/R

How to calculate total current:

  • ITotal = I1 + I2 + . . . In

How to calculate Ohm’s Law:

  • V = IR

Moreover, it’s important to note that if you’re calculating Ohm’s Law to find the current in a single branch, you will need to use the V = I1R1 formula. You can use Ohm’s Law to solve most of the parallel circuit problems if you know the two other values in the formula. For example, V = IR. If you need to calculate the total resistance but know the value of Ohm’s Law and total current, you can use R = V/I. As mentioned previously, the voltage is always the same. Therefore we can assume that VT = V1 = V2 = Vn.

What Are the Disadvantages of Parallel Circuits?

Both series circuits and parallel circuits both have their own advantages and disadvantages, and it’s important to understand the cons inherent in each type of circuit. The main issue with parallel circuits, for example, is the complex design. That is, in a parallel circuit, the current splits into multiple, branching paths. Moreover, “multiple current paths come either from multiple power sources flowing to a single output, or one power source running to multiple outputs.” In the end, this makes their design more complex than most series circuits.

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Additionally, no matter the number of power sources, the voltage across a parallel circuit remains the same. So, if you need different voltages at different points in the circuit, you’ll have to add resistors and other elements to regulate said voltages. Finally, Sciencing also points out that, “When branches are added to a parallel circuit, the voltage is the same across the whole circuit, meaning the the current flow must change to compensate.”

Parallel Circuit Advantages

Each individual element of a parallel circuit creates a connection that has many practicalities in everyday life. When connected in a parallel circuit, bulbs tend to produce a brighter light. Why’s that? Well, all bulbs in a parallel circuit share consistent voltage, whereas, in a series circuit, they share a common current.

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Moreover, in a parallel circuit, the equivalent resistance is also decreased while the current is increased, which is precisely why the bulbs produce a brighter light. However, it’s important to note that this also depends on several other factors, including the luminous flux of the light source.

As previously mentioned, when you install a parallel circuit, you can turn off one appliance, but rest assured that others will still function. Additionally, with a parallel circuit, you can also add or remove more components without changing the voltage. For this reason, electrical contractors prefer a parallel circuit: its simple design makes it both reliable and safe to use. Despite its simplicity of design, however, it’s important that you leave the installment process to a professional.

Parallel Circuit Diagram

Pictured below is a simple parallel circuit diagram in which several resistors (R1, R2, and Rn) that form several paths. In a standard diagram you may come across in school, you’ll notice the paths go from the positive battery terminal to the negative battery terminal. Each individual path is known as a branch.

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All diagrams you see work on the same principle, but the number of components may change depending on the diagram. Remember: a parallel circuit requires two or more components. In some cases, you may notice that a single circuit is a mix of series and parallel wiring. You can solve those combinations by simplifying the circuit to focus on resistors that are connected together first. The best way to stay on top of your circuit calculations is to use a table.