When early scientists started to work with electricity, the structure of atoms was not very clear, and they assumed at that time the current was a flow of positive charges (protons) from the positive terminal of a power supply (such as a battery) to its negative terminal.
Which way does electric charge really flow? Later on, scientists discovered that electric current is in fact a flow of negative charges (electrons) from the negative terminal of a power supply to its positive terminal. But by the time the real direction of current flow was discovered, a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal had already been well established and used commonly in electrical circuitry.
Currently, there are two methods to express the direction of electric current. One is known as the conventional current flow version, in which the current is defined as a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal. The other is called electrons flow version, in which the current is defined as a flow of negative charges (electrons) from the negative terminal of a power supply unit to its positive terminal. These two methods are shown in below Figure
Because the charge or current cannot be seen in electric circuits, it will make no difference as to which method is used, and it will not affect the analysis, design, calculation, measurement and applications of the electric circuits as long as one method is used consistently. In this book, the conventional current flow version is used.
Note:
Conventional current flow is defined as a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal.
Electron flow version is defined as a flow of negative charges (electrons) from the negative terminal of a power supply to its positive terminal.
Source: book
Understandable Electric Circuits (Meizhong Wang)
Which way does electric charge really flow? Later on, scientists discovered that electric current is in fact a flow of negative charges (electrons) from the negative terminal of a power supply to its positive terminal. But by the time the real direction of current flow was discovered, a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal had already been well established and used commonly in electrical circuitry.
Currently, there are two methods to express the direction of electric current. One is known as the conventional current flow version, in which the current is defined as a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal. The other is called electrons flow version, in which the current is defined as a flow of negative charges (electrons) from the negative terminal of a power supply unit to its positive terminal. These two methods are shown in below Figure
Because the charge or current cannot be seen in electric circuits, it will make no difference as to which method is used, and it will not affect the analysis, design, calculation, measurement and applications of the electric circuits as long as one method is used consistently. In this book, the conventional current flow version is used.
Note:
Conventional current flow is defined as a flow of positive charges (protons) from the positive terminal of a power supply to its negative terminal.
Electron flow version is defined as a flow of negative charges (electrons) from the negative terminal of a power supply to its positive terminal.
Source: book
Understandable Electric Circuits (Meizhong Wang)
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