The question of whether voltage flows from positive to negative reveals a common confusion about how electricity moves and what voltage actually represents. Electricity is a system of interacting forces and moving particles. To understand the direction of movement in a circuit, it is necessary to first separate the idea of voltage from the idea of flow. This distinction is the starting point for clarifying the movement of charge in any electrical system. The goal is to define voltage and then explain how it relates to the actual movement of charge carriers, which has two different—but both correct—descriptions.
Understanding Electrical Potential
Voltage is not a substance that travels through a wire but is instead a measure of the potential energy difference between two points in an electrical circuit. This concept is formally known as electrical potential difference and is measured in units called volts. The entire purpose of a power source, like a battery, is to establish and maintain this difference in potential energy. This is analogous to a water tower and ground level, where the height represents the high potential (positive terminal) and the ground represents the low potential (negative terminal). Water flowing from the tower to the ground is driven by this difference in height.
In an electrical context, the positive terminal represents an area of higher electrical potential energy, and the negative terminal represents an area of lower electrical potential energy. This potential difference means that every unit of charge has potential energy available to convert into work, such as lighting a bulb. The voltage measurement tells you precisely how much energy is transferred for every unit of charge that travels between the two points.
The Two Directions of Current Flow
The confusion surrounding electrical direction stems from a historical misunderstanding that resulted in two accepted models of current flow. Long before the electron was discovered, Benjamin Franklin theorized that charge moved from areas of excess to areas of deficit, which he labeled as positive to negative. This historical assumption led to the definition of Conventional Current, which is still used today in most circuit analysis and diagrams, where the current is shown flowing from the positive terminal to the negative terminal.
The actual physical reality of charge movement was revealed with the discovery of the electron, the tiny, negatively charged particle that carries electricity in metal conductors. Because opposite charges attract, these negatively charged electrons are pushed away from the negative terminal and drawn toward the positive terminal. This actual movement of charge is called Electron Flow, and it moves in the opposite direction of conventional current—from the negative terminal to the positive terminal.
The voltage itself does not flow, but the potential difference it creates is what causes the current, or movement of charge, to happen. Both conventional current and electron flow are valid ways to analyze a circuit because the effects of a negative charge moving in one direction are electrically equivalent to a positive charge moving in the opposite direction. Engineers primarily use the conventional current model for circuit design and analysis because it was standardized first.
Voltage Versus Current
To fully grasp electrical circuits, one must maintain a clear distinction between voltage and current. Voltage is the potential difference, acting like the electrical pressure that drives the charge. It is the force that motivates the charge carriers to move, existing even when no movement is occurring, such as when a switch is open. Current, on the other hand, is the actual movement of charge—the rate at which electrical charge flows past a specific point in the circuit.
If voltage is the pressure in a pipe, current is the volume of water flowing through that pipe per second. Current is measured in amperes (amps), representing the number of coulombs of charge passing per second. While one cannot exist without the other in a working circuit, their roles are distinct: voltage creates the condition for flow, and current is the resulting flow. A large voltage means there is a high potential for energy transfer, which will generally result in a large current, provided the path of the circuit allows it.
Visualizing the Electrical Circuit
In a simple closed circuit, such as a battery connected to a light bulb, the battery maintains the necessary voltage potential across the circuit. The battery’s internal chemistry works constantly to keep one terminal at a high potential and the other at a low potential. This potential difference acts across the entire circuit, including the light bulb filament.
The voltage potential is not consumed as it travels, but instead, the energy it represents is converted into work by the components in the circuit. As the charge carriers are driven by this potential difference, they move through the light bulb, where the electrical energy is converted into light and heat. The amount of energy lost by the charge in passing through the bulb is measured as a voltage drop across that component.
This model reinforces that voltage is a static pressure measured between two points, defining the energy available per charge, rather than a substance that moves. The movement of charge (current) is continuous around the circuit, driven by the constant potential difference provided by the source.