Voltage in Parallel Circuits (Sources, Formula & How To Add)

Contents

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Key learnings:

Voltage in Parallel Circuits Definition: A parallel circuit is defined as one where multiple devices are connected side by side, each in its own branch, with the same voltage across each branch.
Current Distribution: The total current in a parallel circuit is the sum of the currents through each branch, allowing multiple paths for current flow.
Resistance Calculation: In parallel circuits, adding more branches decreases the overall resistance, making it easier for the current to flow.
How to Add Voltage in Parallel: The voltage across each device in a parallel circuit is equal to the source voltage, ensuring consistent voltage across all branches.
Advantages and Applications: Parallel circuits are used in homes and various applications because they allow independent operation, full voltage to each device, and isolate faults effectively.

What are Voltages in Parallel?

A parallel circuit or parallel connection exists when two or more electrical devices are linked side by side within a circuit, each occupying its own distinct branch. Voltage (that is, potential difference) is the reason current passes through a closed circuit. This article discusses in detail voltages in a parallel circuit.

In a parallel circuit, several branch lines create multiple pathways for the charge to travel. On reaching a node, the charge divides among the available branches on its way back to the low-potential terminal.

Consider a closed circuit with a voltage source and a single resistor: the current has one pathway. Now add two more resistors in parallel with the first.

The current then has several pathways instead of one for reaching the low-potential terminal. As the number of branches grows, the overall resistance decreases and the total circuit current rises.

In other words, the entire current equals the sum of the currents through the three resistors. The parallel circuit also contains sets of electrically common points. In the circuit shown below these pairs are A-H, B-G, C-F and D-E. The voltage measured across any pair of common points therefore remains equal.

The first figure shows a closed circuit with a voltage source and one resistor; the second shows a parallel circuit with three resistors and a voltage source.

The voltage in this circuit is the same across all three branches, and it also equals the voltage of the source:

The total current in this parallel circuit is represented by I_total, given as

The total or effective resistance of this parallel circuit follows from the formula below.

We can conclude that adding further branches to a parallel circuit increases the total current drawn from the source, which can overload it if the extra demand exceeds its rating.

Advantages of Parallel Circuits

Suppose we want to connect two bulbs to a single battery. They can be wired in series (one after another along a single path) or in parallel. In series, both bulbs share the same conducting path between the two battery terminals, which causes these problems:

We cannot turn on or operate one bulb alone.
Both bulbs run dim because they share the same source.
If one bulb develops a fault, the whole circuit is affected.

Connecting the two bulbs side by side in parallel lets each bulb receive the full voltage from the battery. This setup has several advantages:

Both bulbs get the full amount of voltage of the battery.
We can operate the two bulbs separately.
Both bulbs shine at full brightness when turned on.
If there is a fault in one bulb, it can be removed or repaired without affecting the rest of the circuit.

Parallel Circuits in Home

All the appliances at home connect in parallel with one another. That is why every appliance can operate separately without affecting the others: you can run the washing machine without switching on the microwave or the television.

The electrical cables in a house comprise three wires: live, neutral and earth. For the moment we ignore the earth wire and concentrate only on the live wire and the neutral wire.

A voltage is present between the live and neutral wires, which ultimately connect back to a power plant. Every socket in the house links to this live and neutral pair. Plugging an appliance pin into a socket creates an electrical connection with it.

Each appliance owns its own connection between the live and neutral wires. When we switch a device on, the whole voltage appears across it, so it can be operated independently.