As an expert in the field of electrical engineering, I'm delighted to delve into the intricacies of how current flows in a wire. The concept of electric current is fundamental to the operation of electronic devices and systems. It's a flow of electric charge, and it's governed by the principles of electromagnetism.

In a wire, the flow of current is typically due to the movement of electrons, which are negatively charged particles. However, by convention, the direction of electric current is defined as the direction in which positive charges would move. This convention was established before the discovery of electrons and the understanding that they are the primary charge carriers in most conductors.

The reason for this convention is largely historical and stems from the work of Benjamin Franklin, who assigned the term "positive" to the charge of a glass rod that had been rubbed with silk, and "negative" to the charge of a rubber rod that had been rubbed with fur. This terminology was adopted widely, and it stuck even after the discovery of electrons and the realization that they were the actual charge carriers in metals.

In a typical conductor like copper, which is used in electrical wiring, the atoms are arranged in a lattice structure. Each copper atom contributes one free electron to the conduction process. These electrons are not bound to any particular atom and are free to move throughout the metal lattice. When a voltage is applied across the ends of the wire, it creates an electric field that exerts a force on these free electrons, causing them to drift in a direction opposite to the field.

This movement of electrons constitutes the flow of current. However, because the convention dictates that current flows in the direction of positive charge movement, we say that the current flows from the positive terminal of a battery, through the wire, and towards the negative terminal. In reality, the electrons are moving from the negative terminal to the positive terminal.

It's also important to note that the actual speed at which electrons move in a wire is quite slow, typically on the order of millimeters per second. However, the electric field propagates at nearly the speed of light, which is why electrical devices respond almost instantly when switched on or off.

In summary, the flow of current in a wire is due to the movement of electrons, which are negatively charged. Despite this, the direction of current is defined as the direction that positive charges would move if they were the charge carriers. This historical convention has persisted and is still used today to describe the direction of current flow in electrical circuits.

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The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction.read more >>