An electrical circuit is a complete path that allows electric charge to flow continuously from a power source and back again. The flow of this charge is known as current, and the force pushing it is called voltage. A parallel circuit offers multiple independent paths, or branches, for the current to travel. Understanding how current behaves in these separate branches is necessary to grasp the operation of a parallel circuit configuration.
Voltage Consistency Across Branches
The defining characteristic of any parallel circuit is that the voltage remains identical across every branch. Voltage represents the electrical potential energy difference between two points in a circuit, similar to water pressure in a plumbing system. Since each branch is wired directly across the same two connection points, they all share the exact same potential difference.
Imagine the electrical source, like a battery, providing a certain pressure to push the charge. Every available path is connected at the beginning and end to this same pressure source. Consequently, the voltage drop across a resistor in one branch is the same magnitude as the voltage drop across a resistor in any other parallel branch. This consistent voltage sets the stage for how the current must behave.
How Total Current Divides
The answer to whether the current is the same in a parallel circuit is no; the total current supplied by the source splits up among the multiple paths. This is a direct consequence of the conservation of charge, meaning the total amount of charge entering a junction must equal the total amount of charge leaving it.
The current leaves the power source and travels until it reaches a junction point where the circuit branches off into parallel paths. At this point, the total current divides, with a portion flowing down each branch. The sum of the individual currents flowing through all parallel branches must add up precisely to the total current that originally left the source. The currents then recombine at a later junction before returning to the power source.
Resistance Determines Current Flow
The reason the current divides unevenly is due to the resistance present in each path. Ohm’s Law establishes a relationship between voltage (\(V\)), current (\(I\)), and resistance (\(R\)), expressed as \(I = V/R\). Since the voltage (\(V\)) is constant across all parallel branches, the amount of current (\(I\)) that flows through any single branch is inversely related to its resistance (\(R\)).
This means that a branch offering a lower resistance will allow a greater amount of current to flow through it. Conversely, a branch with a higher resistance will restrict the flow, resulting in a smaller current traveling down that path. For example, if one branch has twice the resistance of another, it will only receive half the current. This demonstrates that the current is only identical in every path if all the resistances are exactly equal.
How Parallel Wiring Affects Total Resistance
Adding more branches in a parallel circuit decreases the overall, or equivalent, resistance of the entire circuit. Each new parallel path opens up an additional route for the charge to flow, making it easier for the current to leave the power source. Even if the added path contains a component with high resistance, the total resistance still drops because the overall capacity for current flow increases. This relationship is expressed by a reciprocal formula, where the sum of the reciprocals of the individual resistances equals the reciprocal of the total resistance.