Why do we say current flows from positive to negative?
2 Answers
The convention that current flows from positive to negative has its roots in historical practices and conventions in electrical engineering. Let’s break down the reasons for this:
### Historical Background
1. **Benjamin Franklin's Convention**: The idea of electric current flow from positive to negative originated with Benjamin Franklin in the 18th century. Franklin defined electric charge as having two types: positive and negative. He chose to call the charge that flows from a positive source to a negative sink "positive current." This choice was largely arbitrary; it could just as easily have been the other way around.
2. **Fixed Convention**: Despite later discoveries that showed the actual charge carriers in many materials (especially metals) are electrons, which move from negative to positive, the convention of positive-to-negative current flow remained in use. This is because changing the convention would have involved significant revision of existing literature and practices, so it was maintained for consistency.
### Understanding Current Flow
1. **Conventional Current Direction**: In the context of conventional current, we follow Franklin’s convention: current is considered to flow from the positive terminal of a power source to the negative terminal. This is useful for circuit analysis and design because it provides a consistent framework for discussing how current flows through components.
2. **Electron Flow**: In most conductive materials, such as metals, the actual charge carriers are electrons, which are negatively charged. These electrons move from the negative terminal (where there is an excess of electrons) to the positive terminal (where there is a deficit of electrons). This is referred to as "electron flow" and is in the opposite direction to conventional current.
### Why Keep the Convention?
1. **Consistency in Analysis**: The use of conventional current simplifies the analysis of electrical circuits. For decades, this convention has been deeply embedded in textbooks, standards, and practices. Changing it would complicate communication and documentation.
2. **Mathematical Framework**: Most of the laws and equations in circuit theory (like Ohm’s Law, Kirchhoff’s Laws) are framed with conventional current flow in mind. While the underlying physical processes involve electrons moving, the mathematics and theory work seamlessly with the conventional direction.
### Summary
In summary, the convention of current flowing from positive to negative is based on historical choices made by Benjamin Franklin and has been retained for consistency and simplicity in electrical engineering practices. Although the physical reality of charge flow (electron movement) is opposite to this convention, using the positive-to-negative direction remains a standard practice for theoretical and practical purposes.
### Historical Background
1. **Benjamin Franklin's Convention**: The idea of electric current flow from positive to negative originated with Benjamin Franklin in the 18th century. Franklin defined electric charge as having two types: positive and negative. He chose to call the charge that flows from a positive source to a negative sink "positive current." This choice was largely arbitrary; it could just as easily have been the other way around.
2. **Fixed Convention**: Despite later discoveries that showed the actual charge carriers in many materials (especially metals) are electrons, which move from negative to positive, the convention of positive-to-negative current flow remained in use. This is because changing the convention would have involved significant revision of existing literature and practices, so it was maintained for consistency.
### Understanding Current Flow
1. **Conventional Current Direction**: In the context of conventional current, we follow Franklin’s convention: current is considered to flow from the positive terminal of a power source to the negative terminal. This is useful for circuit analysis and design because it provides a consistent framework for discussing how current flows through components.
2. **Electron Flow**: In most conductive materials, such as metals, the actual charge carriers are electrons, which are negatively charged. These electrons move from the negative terminal (where there is an excess of electrons) to the positive terminal (where there is a deficit of electrons). This is referred to as "electron flow" and is in the opposite direction to conventional current.
### Why Keep the Convention?
1. **Consistency in Analysis**: The use of conventional current simplifies the analysis of electrical circuits. For decades, this convention has been deeply embedded in textbooks, standards, and practices. Changing it would complicate communication and documentation.
2. **Mathematical Framework**: Most of the laws and equations in circuit theory (like Ohm’s Law, Kirchhoff’s Laws) are framed with conventional current flow in mind. While the underlying physical processes involve electrons moving, the mathematics and theory work seamlessly with the conventional direction.
### Summary
In summary, the convention of current flowing from positive to negative is based on historical choices made by Benjamin Franklin and has been retained for consistency and simplicity in electrical engineering practices. Although the physical reality of charge flow (electron movement) is opposite to this convention, using the positive-to-negative direction remains a standard practice for theoretical and practical purposes.